U.S. patent application number 12/531414 was filed with the patent office on 2010-04-08 for polymer electrolyte fuel cell and fuel cell stack including the same.
Invention is credited to Miho Gemba, Shinsuke Takeguchi, Yoichiro Tsuji.
Application Number | 20100086819 12/531414 |
Document ID | / |
Family ID | 39863518 |
Filed Date | 2010-04-08 |
United States Patent
Application |
20100086819 |
Kind Code |
A1 |
Gemba; Miho ; et
al. |
April 8, 2010 |
POLYMER ELECTROLYTE FUEL CELL AND FUEL CELL STACK INCLUDING THE
SAME
Abstract
A polymer electrolyte fuel cell includes: a membrane-electrode
assembly (10) having a polymer electrolyte membrane (1) and a pair
of electrodes (4, 8) sandwiching a portion of the polymer
electrolyte membrane (1) which portion is located inwardly of a
peripheral portion of the polymer electrolyte membrane (1); an
electrically-conductive first separator (30) disposed to contact
the membrane-electrode assembly (10) and formed such that a
groove-like first reactant gas channel (37) is formed on one main
surface thereof so as to bend; and an electrically-conductive
second separator (20) disposed to contact the membrane-electrode
assembly (10) and formed such that a groove-like second reactant
gas channel (27) is formed on one main surface thereof so as to
bend, wherein the first reactant gas channel (27) is formed such
that a width of a portion of the first reactant gas channel (27)
which portion is formed at least a portion (hereinafter referred to
as an uppermost stream portion 8C of the first separator 30)
located between a portion where the first reactant gas channel (27)
extending from an upstream end thereof first contacts the electrode
8 and a portion where the second reactant gas channel (27)
extending from an upstream end thereof first contacts the electrode
4 is smaller than a width of a portion of the first reactant gas
channel (27) which portion is formed at a portion other than the
uppermost stream portion 8C of the first separator 30.
Inventors: |
Gemba; Miho; (Osaka, JP)
; Tsuji; Yoichiro; (Osaka, JP) ; Takeguchi;
Shinsuke; (Osaka, JP) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, NW
WASHINGTON
DC
20005-3096
US
|
Family ID: |
39863518 |
Appl. No.: |
12/531414 |
Filed: |
March 17, 2008 |
PCT Filed: |
March 17, 2008 |
PCT NO: |
PCT/JP2008/000613 |
371 Date: |
September 15, 2009 |
Current U.S.
Class: |
429/454 |
Current CPC
Class: |
H01M 8/241 20130101;
Y02E 60/50 20130101; H01M 8/0258 20130101; H01M 8/026 20130101;
H01M 8/0267 20130101; H01M 8/04291 20130101; H01M 8/0263 20130101;
H01M 8/2457 20160201; H01M 8/0265 20130101; H01M 2008/1095
20130101; H01M 8/1007 20160201 |
Class at
Publication: |
429/26 ; 429/30;
429/34 |
International
Class: |
H01M 8/04 20060101
H01M008/04; H01M 8/10 20060101 H01M008/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2007 |
JP |
2007-066860 |
Claims
1. A polymer electrolyte fuel cell comprising: a membrane-electrode
assembly including a polymer electrolyte membrane and a pair of
electrodes sandwiching a portion of the polymer electrolyte
membrane which portion is located inwardly of a peripheral portion
of the polymer electrolyte membrane; an electrically-conductive
first separator having a plate shape, disposed to contact the
membrane-electrode assembly, and formed such that a groove-like
first reactant gas channel is formed on one main surface thereof
contacting the electrode so as to bend; and an
electrically-conductive second separator having a plate shape,
disposed to contact the membrane-electrode assembly, and formed
such that a groove-like second reactant gas channel is formed on
one main surface thereof contacting the electrode so as to bend,
wherein the first reactant gas channel is formed such that when
viewed from a thickness direction of the first separator, a width
of a portion (hereinafter referred to as an uppermost stream
portion) of the first reactant gas channel which portion extends at
least from a portion where the first reactant gas channel extending
from an upstream end thereof first contacts the electrode to a
portion where the first reactant gas channel overlapping the second
reactant gas channel first separates from the second reactant gas
channel is smaller than a width of a portion of the first reactant
gas channel which portion is a portion other than the uppermost
stream portion of the first reactant gas channel.
2. The polymer electrolyte fuel cell according to claim 1, wherein
the second reactant gas channel is formed such that when viewed
from a thickness direction of the second separator, a width of a
portion of the second reactant gas channel which portion is formed
at least a portion (hereinafter referred to as an uppermost stream
portion of the second separator) located between the portion where
the second reactant gas channel extending from the upstream end
thereof first contacts the electrode and the portion where the
first reactant gas channel extending from the upstream end thereof
first contacts the electrode is smaller than a width of a portion
of the second reactant gas channel which portion is formed at a
portion other than the uppermost stream portion of the second
separator.
3. (canceled)
4. The polymer electrolyte fuel cell according to claim 1, wherein
the second reactant gas channel is formed such that when viewed
from a thickness direction of the second separator, a width of a
portion (hereinafter referred to as an uppermost stream portion) of
the second reactant gas channel which portion extends at least from
the portion where the second reactant gas channel extending from
the upstream end thereof first contacts the electrode to a portion
where the second reactant gas channel overlapping the first
reactant gas channel first separates from the first reactant gas
channel is smaller than a width of a portion of the second reactant
gas channel which portion is a portion other than the uppermost
stream portion of the second reactant gas channel.
5. The polymer electrolyte fuel cell according to claim 1, wherein
a depth of the uppermost stream portion of the first reactant gas
channel is larger than a depth of a portion other than the
uppermost stream portion of the first reactant gas channel.
6. The polymer electrolyte fuel cell according to claim 2, wherein
a depth of the uppermost stream portion of the second reactant gas
channel is larger than a depth of a portion other than the
uppermost stream portion of the second reactant gas channel.
7. The polymer electrolyte fuel cell according to claim 1, wherein
a cross-sectional area of the uppermost stream portion of the first
reactant gas channel is substantially the same as a cross-sectional
area of a portion other than the uppermost stream portion of the
first reactant gas channel.
8. The polymer electrolyte fuel cell according to claim 2, wherein
a cross-sectional area of the uppermost stream portion of the
second reactant gas channel is substantially the same as a
cross-sectional area of a portion other than the uppermost stream
portion of the second reactant gas channel.
9. The polymer electrolyte fuel cell according to claim 1, wherein
among rib portions each formed between adjacent portions of the
first reactant gas channel, a rib portion formed by the uppermost
stream portion has a width larger than a width of the other rib
portion.
10. The polymer electrolyte fuel cell according to claim 2, wherein
among rib portions each formed between adjacent portions of the
second reactant gas channel, a rib portion formed by the uppermost
stream portion has a width larger than a width of the other rib
portion.
11. The polymer electrolyte fuel cell according to claim 1,
wherein: a groove-like cooling fluid channel is formed on the other
main surface of the first separator and/or the other main surface
of the second separator; and each of a dew point of a first
reactant gas flowing through the first reactant gas channel and a
dew point of a second reactant gas flowing through the second
reactant gas channel is lower than a temperature of a cooling fluid
flowing through the cooling fluid channel.
12. The polymer electrolyte fuel cell according to claim 1, wherein
each of the first separator and the second separator is provided
with a first reactant gas supplying manifold hole and a second
reactant gas supplying manifold hole which are formed to penetrate
therethrough in a thickness direction and be opposed to each
other.
13. The polymer electrolyte fuel cell according to claim 1, wherein
the first reactant gas channel and the second reactant gas channel
are formed to realize parallel flow.
14. The polymer electrolyte fuel cell according to claim 1, wherein
the first reactant gas channel and/or the second reactant gas
channel is formed in a serpentine shape.
15. The polymer electrolyte fuel cell according to claim 1, wherein
the first reactant gas channel and/or the second reactant gas
channel is formed in a spiral shape.
16. The polymer electrolyte fuel cell according to claim 1, wherein
the width of the entire uppermost stream portion of the first
reactant gas channel is smaller than a with of an entire portion
(hereinafter referred to as a remaining portion) other than the
uppermost stream portion of the first reactant gas channel.
17. The polymer electrolyte fuel cell according to claim 16,
wherein the width of the entire remaining portion of the first
reactant gas channel is constant.
18. The polymer electrolyte fuel cell according to claim 16,
wherein the width of the entire uppermost stream portion of the
first reactant gas channel is constant.
19. The polymer electrolyte fuel cell according to claim 4, wherein
the width of the entire uppermost stream portion of the second
reactant gas channel is smaller than a width of an entire portion
other than the uppermost stream portion of the second reactant gas
channel.
20. The polymer electrolyte fuel cell according to claim 19,
wherein the width of the entire remaining portion of the second
reactant gas channel is constant.
21. The polymer electrolyte fuel cell according to claim 19,
wherein the width of the entire uppermost stream portion of the
second reactant gas channel is constant.
22. A fuel cell stack configured such that a plurality of the
polymer electrolyte fuel cells according to claim 1 are stacked and
fastened.
Description
TECHNICAL FIELD
[0001] The present invention relates to the configuration of a
polymer electrolyte fuel cell and the configuration of a fuel cell
stack including the polymer electrolyte fuel cell.
BACKGROUND ART
[0002] In recent years, a fuel cell is attracting attention as a
clean energy source. One example of the fuel cell is a polymer
electrolyte fuel cell. The polymer electrolyte fuel cell
(hereinafter referred to as "PEFC") includes a membrane-electrode
assembly, and an anode separator and a cathode separator disposed
to sandwich the membrane-electrode assembly and respectively
contact an anode and a cathode. The membrane-electrode assembly
includes the anode and the cathode (each of which is referred to as
"electrode") each constituted by a gas diffusion layer and a
catalyst layer. The gas diffusion layer has fine holes that are
flow paths of a reactant gas. A fuel gas channel is formed on one
main surface of the anode separator. An oxidizing gas channel is
formed on one main surface of the cathode separator. A fuel gas
(hydrogen) supplied through the fuel gas channel to the anode is
ionized (H.sup.+), flows through the gas diffusion layer and
catalyst layer of the anode, further flows through the polymer
electrolyte membrane via water, and moves to the cathode. The
hydrogen ion having reached the cathode generates water through the
following electric power generating reaction in the catalyst layer
of the cathode.
Anode: H.sub.2.fwdarw.2H.sup.++2e.sup.-
Cathode: (1/2)O.sub.2+2H.sup.++2e.sup.-.fwdarw.H.sub.2O
Total Reaction: H.sub.2+(1/2)O.sub.2.fwdarw.H.sub.2O
[0003] The water (generated water) generated as above flows to the
oxidizing gas channel of the cathode separator as steam or liquid.
Moreover, a part of the water generated in the cathode moves to the
anode (so-called "back diffusion"). Therefore, as each of the
oxidizing gas and the fuel gas (each of which is referred to as
"reactant gas") flows from an upstream portion to downstream
portion of each of the oxidizing gas channel and the fuel gas
channel, a partial pressure of steam in each of the oxidizing gas
and the fuel gas increases. With this, especially when the fuel
cell is driven at high temperature and high humidity (for example,
the dew point of the reactant gas is set to be the same as the
temperature inside the fuel cell stack), flooding occurs by
clogging of the generated water in the downstream portion of the
oxidizing gas channel or the fuel gas channel or by clogging of the
generated water in the fine holes of the gas diffusion layer
opposed to the oxidizing gas channel or the fuel gas channel.
[0004] Disclosed as one example of a technology for suppressing the
occurrence of the flooding is a fuel cell in which at least one of
the depth and width of the oxidizing gas channel is gradually
reduced from an upstream channel region to downstream channel
region of the oxidizing gas channel (see Patent Document 1 for
example). In accordance with such fuel cell, the flow velocity of
the oxidizing gas flowing through the downstream channel region of
the oxidizing gas channel increases, so that the generated water
clogged in the oxidizing gas channel can be discharged.
[0005] Patent Document 1: Japanese Laid-Open Patent Application
Publication 6-267564
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0006] However, in accordance with the configuration of Patent
Document 1, when the fuel cell is driven at high temperature and
high humidity, the generated water clogged in the fine holes of the
gas diffusion layer cannot be removed, so that the flooding is not
adequately suppressed.
[0007] Moreover, in accordance with the configuration of Patent
Document 1, when the fuel cell is driven at high temperature and
low humidity (for example, the dew point of the reactant gas is set
to be lower than the temperature inside the fuel cell stack), the
above reaction is not adequately carried out in the upstream
portion of the reactant gas channel, so that the water may not be
generated, a portion of the polymer electrolyte membrane which
portion is opposed to the upstream portion of the reactant gas
channel may dry, and the membrane may deteriorate.
[0008] The present invention was made to solve the above problems,
and an object of the present invention is to provide a polymer
electrolyte fuel cell capable of adequately suppressing the
flooding when the polymer electrolyte fuel cell is driven at high
temperature and high humidity, and a fuel cell stack including the
polymer electrolyte fuel cell. Another object of the present
invention is to provide a polymer electrolyte fuel cell capable of
suppressing the deterioration of the polymer electrolyte membrane
when the polymer electrolyte fuel cell is driven at high
temperature and low humidity, and a fuel cell stack including the
polymer electrolyte fuel cell.
Means for Solving the Problems
[0009] It is known that during the operation of the fuel cell, the
water (water in liquid form and gas form) content of a portion of a
gas diffusion electrode (hereinafter referred to as "electrode")
which portion faces the reactant gas channel is lower than the
water content of a portion of the electrode which portion contacts
a rib portion formed between adjacent portions of the reactant gas
channel. FIG. 15 is a schematic diagram showing the water content
of the electrode during the operation of the fuel cell.
[0010] As a result of diligent studies to solve the above problems
of the prior art, the present inventors have found the following
points. To be specific, as shown in FIG. 15, the present inventors
have found that the water existing in a portion 202A of an
electrode 202 which portion contacts a rib portion 204 formed
between adjacent portions of a reactant gas channel 203 diffuses to
a portion 202B of the electrode 202 which portion faces the
reactant gas channel 203, and the water content of a portion of the
electrode 202 which portion is located in the vicinity of a
boundary between the rib portion 204 and the reactant gas channel
203 becomes higher than that of a center portion of the portion
202B of the electrode 202. In other words, the present inventors
have found that the water content of a portion of the electrode 202
decreases as the portion is away from the portion 202A of the
electrode 202 which portion contacts the rib portion 204. Then, the
present inventors have found that adopting the below-described
configuration is highly effective to achieve the objects of the
present invention. Thus, the present invention has been
achieved.
[0011] To be specific, a polymer electrolyte fuel cell according to
the present invention includes: a membrane-electrode assembly
including a polymer electrolyte membrane and a pair of electrodes
sandwiching a portion of the polymer electrolyte membrane which
portion is located inwardly of a peripheral portion of the polymer
electrolyte membrane; an electrically-conductive first separator
having a plate shape, disposed to contact the membrane-electrode
assembly, and formed such that a groove-like first reactant gas
channel is formed on one main surface thereof contacting the
electrode so as to bend; and an electrically-conductive second
separator having a plate shape, disposed to contact the
membrane-electrode assembly, and formed such that a groove-like
second reactant gas channel is formed on one main surface thereof
contacting the electrode so as to bend, wherein the first reactant
gas channel is formed such that when viewed from a thickness
direction of the first separator, a width of a portion of the first
reactant gas channel which portion is formed at least a portion
(hereinafter referred to as an uppermost stream portion of the
first separator) located between a portion where the first reactant
gas channel extending from an upstream end thereof first contacts
the electrode and a portion where the second reactant gas channel
extending from an upstream end thereof first contacts the electrode
is smaller than a width of a portion of the first reactant gas
channel which portion is formed at a portion other than the
uppermost stream portion of the first separator.
[0012] As described above, the water content of a portion of the
electrode which portion faces the first reactant gas channel is
lower than the water content of a portion of the electrode which
portion contacts the rib portion. However, in the present
invention, the first reactant gas channel is formed such that the
width of the portion of the first reactant gas channel which
portion is formed at the uppermost stream portion of the first
separator is smaller than the width of the portion of the first
reactant gas channel which portion is formed at a portion other
than the uppermost stream portion of the first separator. On this
account, the portion (hereinafter referred to as an uppermost
stream portion of the electrode) whose water content is low and
which faces the channel formed at the uppermost stream portion of
the first separator is small in size. Therefore, especially when
the polymer electrolyte fuel cell according to the present
invention is driven at high temperature and low humidity, the
drying of the uppermost stream portion of the electrode can be
suppressed, and therefore, the drying of a portion of the polymer
electrolyte membrane which portion is opposed to the uppermost
stream portion of the first reactant gas channel can be suppressed,
so that the deterioration of the polymer electrolyte membrane can
be suppressed.
[0013] Meanwhile, the width of a portion of the first reactant gas
channel which portion is formed at a portion other than the
uppermost stream portion of the first separator is larger than the
width of a portion of the first reactant gas channel which portion
is formed at the uppermost stream portion of the first separator.
Therefore, the water content of the portion (hereinafter referred
to as a downstream portion of the electrode) facing the channel
formed at a portion other than the uppermost stream portion of the
first separator becomes low. With this, especially when the polymer
electrolyte fuel cell according to the present invention is driven
at high temperature and high humidity, the flooding at the
downstream portion of the electrode (to be precise, the gas
diffusion layer constituting the electrode) can be suppressed.
[0014] Moreover, in the polymer electrolyte fuel cell according to
the present invention, the second reactant gas channel may be
formed such that when viewed from a thickness direction of the
second separator, a width of a portion of the second reactant gas
channel which portion is formed at least a portion (hereinafter
referred to as an uppermost stream portion of the second separator)
located between the portion where the second reactant gas channel
extending from the upstream end thereof first contacts the
electrode and the portion where the first reactant gas channel
extending from the upstream end thereof first contacts the
electrode is smaller than a width of a portion of the second
reactant gas channel which portion is formed at a portion other
than the uppermost stream portion of the second separator.
[0015] With this, especially when the polymer electrolyte fuel cell
according to the present invention is driven at high temperature
and low humidity, the drying of the portion of the polymer
electrolyte membrane which portion is opposed to the channel formed
at the uppermost stream portion of the second separator can be
suppressed. Moreover, especially when the polymer electrolyte fuel
cell according to the present invention is driven at high
temperature and high humidity, the flooding at the downstream
portion of the electrode can be suppressed.
[0016] Moreover, in the polymer electrolyte fuel cell according to
the present invention, the first reactant gas channel may be formed
such that when viewed from the thickness direction of the first
separator, a width of a portion (hereinafter referred to as an
uppermost stream portion) of the first reactant gas channel which
portion extends at least from the portion where the first reactant
gas channel extending from the upstream end thereof first contacts
the electrode to a portion where the first reactant gas channel
overlapping the second reactant gas channel first separates from
the second reactant gas channel is smaller than a width of a
portion of the first reactant gas channel which portion is a
portion other than the uppermost stream portion of the first
reactant gas channel.
[0017] As described above, the water content of a portion of the
electrode which portion faces the first reactant gas channel is
lower than the water content of a portion of the electrode which
portion contacts the rib portion. However, in the present
invention, the width of the uppermost stream portion of the first
reactant gas channel is smaller than the width of a portion other
than the uppermost stream portion of the first reactant gas
channel. On this account, the portion (hereinafter referred to as
an uppermost stream portion of the electrode) whose water content
is low and which faces the uppermost stream portion of the first
reactant gas channel is small in size. Therefore, especially when
the polymer electrolyte fuel cell according to the present
invention is driven at high temperature and low humidity, the
drying of the uppermost stream portion of the electrode can be
suppressed, and therefore, the drying of a portion of the polymer
electrolyte membrane which portion is opposed to the uppermost
stream portion of the first reactant gas channel can be suppressed,
so that the deterioration of the polymer electrolyte membrane can
be suppressed.
[0018] Meanwhile, the width of the portion other than the uppermost
stream portion of the first reactant gas channel is larger than the
width of the uppermost stream portion of the first reactant gas
channel. Therefore, the water content of the portion (hereinafter
referred to as a downstream portion of the electrode) facing the
portion other than the uppermost stream portion of the first
reactant gas channel becomes low. With this, especially when the
polymer electrolyte fuel cell according to the present invention is
driven at high temperature and high humidity, the flooding at the
downstream portion of the electrode (to be precise, the gas
diffusion layer constituting the electrode) can be suppressed.
[0019] Moreover, in the polymer electrolyte fuel cell according to
the present invention, the second reactant gas channel may be
formed such that when viewed from a thickness direction of the
second separator, a width of a portion (hereinafter referred to as
an uppermost stream portion) of the second reactant gas channel
which portion extends at least from the portion where the second
reactant gas channel extending from the upstream end thereof first
contacts the electrode to a portion where the second reactant gas
channel overlapping the first reactant gas channel first separates
from the first reactant gas channel is smaller than a width of a
portion of the second reactant gas channel which portion is a
portion other than the uppermost stream portion of the second
reactant gas channel.
[0020] With this, especially when the polymer electrolyte fuel cell
according to the present invention is driven at high temperature
and low humidity, the drying of the portion of the polymer
electrolyte membrane which portion is opposed to the uppermost
stream portion of the second reactant gas channel can be
suppressed. Moreover, especially when the polymer electrolyte fuel
cell according to the present invention is driven at high
temperature and high humidity, the flooding at the downstream
portion of the electrode can be suppressed.
[0021] Moreover, in the polymer electrolyte fuel cell according to
the present invention, a depth of the uppermost stream portion of
the first reactant gas channel may be larger than a depth of a
portion other than the uppermost stream portion of the first
reactant gas channel.
[0022] Moreover, in the polymer electrolyte fuel cell according to
the present invention, a depth of the uppermost stream portion of
the second reactant gas channel may be larger than a depth of a
portion other than the uppermost stream portion of the second
reactant gas channel.
[0023] Moreover, in the polymer electrolyte fuel cell according to
the present invention, a cross-sectional area of the uppermost
stream portion of the first reactant gas channel may be
substantially the same as a cross-sectional area of a portion other
than the uppermost stream portion of the first reactant gas
channel.
[0024] Moreover, in the polymer electrolyte fuel cell according to
the present invention, a cross-sectional area of the uppermost
stream portion of the second reactant gas channel may be
substantially the same as a cross-sectional area of a portion other
than the uppermost stream portion of the second reactant gas
channel.
[0025] Moreover, in the polymer electrolyte fuel cell according to
the present invention, among rib portions each formed between
adjacent portions of the first reactant gas channel, a rib portion
formed by the uppermost stream portion may have a width larger than
a width of the other rib portion.
[0026] With this configuration, in the portion other than the
uppermost stream portion of the first reactant gas channel, the
contact area between the rib portion of the first separator and the
electrode becomes small. Therefore, the heat generated by the
electric power generating reaction is less likely to be transferred
to the first separator. With this, the heat release to the first
separator is suppressed, so that the portion other than the
uppermost stream portion of the first reactant gas channel is
increased in temperature. Therefore, although the generated water
is accumulated and the steam partial pressure increases at the
portion other than the uppermost stream portion of the first
reactant gas channel, the dew condensation of the water generated
by the electric power generating reaction is less likely to occur,
and the occurrence of the flooding is suppressed at not only the
portion other than the uppermost stream portion of the first
reactant gas channel but also a portion of the gas diffusion layer
of the electrode which portion faces the portion other than the
uppermost stream portion of the first reactant gas channel.
[0027] Meanwhile, in the uppermost stream portion of the first
reactant gas channel, current concentration may occur since the
amount of the reactant gas related to a battery reaction is large,
and in accordance with the conventional configuration, a battery
voltage may decrease due to the increase in a contact resistance.
However, as in the polymer electrolyte fuel cell of the present
invention, by increasing the contact area between the rib portion
and the electrode in the uppermost stream portion of the first
reactant gas channel, the contact resistance is reduced, and the
decrease in the battery voltage is suppressed.
[0028] The area of the rib portion per unit area may be changed
(reduced) from the uppermost stream portion to the downstream
portion of the first reactant gas channel.
[0029] Moreover, in the polymer electrolyte fuel cell according to
the present invention, among rib portions each formed between
adjacent portions of the second reactant gas channel, a rib portion
formed by the uppermost stream portion may have a width larger than
a width of the other rib portion.
[0030] With this configuration, in the portion other than the
uppermost stream portion of the second reactant gas channel, the
contact area between the rib portion of the second separator and
the electrode becomes small. Therefore, the heat generated by the
electric power generating reaction is less likely to be transferred
to the first separator. With this, the heat release to the second
separator is suppressed, so that the portion other than the
uppermost stream portion of the second reactant gas channel is
increased in temperature. Therefore, although the generated water
is accumulated and the steam partial pressure increases at the
portion other than the uppermost stream portion of the second
reactant gas channel, the dew condensation of the water generated
by the electric power generating reaction is less likely to occur,
and the occurrence of the flooding is suppressed at not only the
portion other than the uppermost stream portion of the second
reactant gas channel but also a portion of the gas diffusion layer
of the electrode which portion faces the portion other than the
uppermost stream portion of the second reactant gas channel.
[0031] Meanwhile, in the uppermost stream portion of the second
reactant gas channel, current concentration may occur since the
amount of the reactant gas related to the battery reaction is
large, and in accordance with the conventional configuration, the
battery voltage may decrease due to the increase in the contact
resistance. However, as in the polymer electrolyte fuel cell of the
present invention, by increasing the contact area between the rib
portion and the electrode in the uppermost stream portion of the
second reactant gas channel, the contact resistance is reduced, and
the decrease in the battery voltage is suppressed.
[0032] The area of the rib portion per unit area may be changed
(reduced) from the uppermost stream portion to the downstream
portion of the second reactant gas channel.
[0033] Moreover, in the polymer electrolyte fuel cell according to
the present invention, a groove-like cooling fluid channel may be
formed on the other main surface of the first separator and/or the
other main surface of the second separator, and each of a dew point
of a first reactant gas flowing through the first reactant gas
channel and a dew point of a second reactant gas flowing through
the second reactant gas channel may be lower than a temperature of
a cooling fluid flowing through the cooling fluid channel.
[0034] Moreover, in the polymer electrolyte fuel cell according to
the present invention, each of the first separator and the second
separator may be provided with a first reactant gas supplying
manifold hole and a second reactant gas supplying manifold hole
which are formed to penetrate therethrough in a thickness direction
and be opposed to each other.
[0035] Moreover, in the polymer electrolyte fuel cell according to
the present invention, the first reactant gas channel and the
second reactant gas channel may be formed to realize parallel
flow.
[0036] Moreover, in the polymer electrolyte fuel cell according to
the present invention, the first reactant gas channel and/or the
second reactant gas channel may be formed in a serpentine
shape.
[0037] Moreover, in the polymer electrolyte fuel cell according to
the present invention, the first reactant gas channel and/or the
second reactant gas channel may be formed in a spiral shape.
[0038] Moreover, in the polymer electrolyte fuel cell according to
the present invention, the width of the entire uppermost stream
portion of the first reactant gas channel may be smaller than a
with of an entire portion (hereinafter referred to as a remaining
portion) other than the uppermost stream portion of the first
reactant gas channel.
[0039] Moreover, in the polymer electrolyte fuel cell according to
the present invention, the width of the entire remaining portion of
the first reactant gas channel may be constant.
[0040] Moreover, in the polymer electrolyte fuel cell according to
the present invention, the width of the entire uppermost stream
portion of the first reactant gas channel may be constant.
[0041] Moreover, in the polymer electrolyte fuel cell according to
the present invention, the width of the entire uppermost stream
portion of the second reactant gas channel may be smaller than a
width of an entire portion other than the uppermost stream portion
of the second reactant gas channel.
[0042] Moreover, in the polymer electrolyte fuel cell according to
the present invention, the width of the entire remaining portion of
the second reactant gas channel may be constant.
[0043] Further, in the polymer electrolyte fuel cell according to
the present invention, the width of the entire uppermost stream
portion of the second reactant gas channel may be constant.
[0044] Moreover, a fuel cell stack according to the present
invention is configured such that a plurality of the polymer
electrolyte fuel cells according to claim 1 are stacked and
fastened.
[0045] The above object, other objects, features and advantages of
the present invention will be made clear by the following detailed
explanation of preferred embodiments with reference to the attached
drawings.
EFFECTS OF THE INVENTION
[0046] The polymer electrolyte fuel cell and the fuel cell stack of
the present invention are configured as above. Therefore, when the
polymer electrolyte fuel cell or the fuel cell stack is driven at
high temperature and high humidity, the clogging of the generated
water in not only the reactant gas channel but also the gas
diffusion layer can be prevented, so that the occurrence of the
flooding can be adequately suppressed. Moreover, in accordance with
the polymer electrolyte fuel cell and the fuel cell stack of the
present invention, when the polymer electrolyte fuel cell or the
fuel cell stack is driven at high temperature and low humidity, the
drying of the polymer electrolyte membrane can be suppressed, so
that the deterioration of the polymer electrolyte membrane can be
suppressed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 is a partial cross-sectional view showing the
configuration of a fuel cell of Embodiment 1 of the present
invention.
[0048] FIG. 2 are diagrams showing the configurations of both main
surfaces of a cathode separator used in the fuel cell of FIG. 1.
FIG. 1(a) is a plan view showing the main surface on which an
oxidizing gas channel is formed. FIG. 2(b) is a plan view showing
the main surface on which a cooling fluid channel is formed.
[0049] FIG. 3 are diagrams showing the configurations of both main
surfaces of an anode separator used in the fuel cell of FIG. 1.
FIG. 3(a) is a plan view showing the main surface on which a fuel
gas channel is formed. FIG. 3(b) is a plan view showing the main
surface on which a cooling fluid channel is formed.
[0050] FIG. 4 is a partial cross-sectional view showing the
configuration of the fuel cell of Comparative Example.
[0051] FIG. 5 are diagrams showing the configurations of both main
surfaces of the cathode separator used in the fuel cell of FIG. 4.
FIG. 5(a) is a plan view showing the main surface on which the
oxidizing gas channel is formed. FIG. 5(b) is a plan view showing
the main surface on which the cooling fluid channel is formed.
[0052] FIG. 6 are diagrams showing temperature distributions of
respective portions of the fuel cell. FIG. 6(a) shows the
temperature distributions of respective portions in the cross
section of the fuel cell of Embodiment 1. FIG. 6(b) shows the
temperature distributions of respective portions in the cross
section of the fuel cell of Comparative Example.
[0053] FIG. 7 is a partial cross-sectional view showing the
configuration of the fuel cell of Modification Example 1 of the
present invention.
[0054] FIG. 8 are diagrams showing the configurations of both main
surfaces of the anode separator used in the fuel cell of FIG. 7.
FIG. 8(a) is a plan view showing the main surface on which the fuel
gas channel is formed. FIG. 8(b) is a plan view showing the main
surface on which the cooling fluid channel is formed.
[0055] FIG. 9 is a partial cross-sectional view showing the
configuration of the fuel cell of Modification Example 2 of the
present invention.
[0056] FIG. 10 is a partial cross-sectional view showing the
configuration of the fuel cell of Embodiment 2 of the present
invention.
[0057] FIG. 11 are diagrams showing the configurations of both main
surfaces of the cathode separator used in the fuel cell of FIG. 10.
FIG. 11(a) is a plan view showing the main surface on which the
oxidizing gas channel is formed. FIG. 11(b) is a plan view showing
the main surface on which the cooling fluid channel is formed.
[0058] FIG. 12 is a partial cross-sectional view showing the
configuration of the fuel cell of Embodiment 3 of the present
invention.
[0059] FIG. 13 are diagrams showing the configurations of both main
surfaces of the cathode separator used in the fuel cell of FIG. 12.
FIG. 13(a) is a plan view showing the main surface on which the
oxidizing gas channel is formed. FIG. 13(b) is a plan view showing
the main surface on which the cooling fluid channel is formed.
[0060] FIG. 14 are diagrams showing the configurations of both main
surfaces of the cathode separator used in the fuel cell of
Embodiment 4 of the present invention. FIG. 14(a) is a plan view
showing the main surface on which the oxidizing gas channel is
formed. FIG. 14(b) is a plan view showing the main surface on which
the cooling fluid channel is formed.
[0061] FIG. 15 is a schematic diagram showing the water content of
the electrode during the operation of the fuel cell.
[0062] FIG. 16 is a perspective view schematically showing a
schematic configuration of a fuel cell stack according to
Embodiment 5 of the present invention.
[0063] FIG. 17 is a cross-sectional view schematically showing a
schematic configuration of the fuel cell in the fuel cell stack
shown in FIG. 16.
[0064] FIG. 18 is a schematic diagram showing a schematic
configuration of the anode separator of the fuel cell shown in FIG.
17.
[0065] FIG. 19 is a schematic diagram showing a schematic
configuration of the cathode separator of the fuel cell shown in
FIG. 17.
[0066] FIG. 20 is a schematic diagram showing the configurations of
the anode separator and cathode separator of the fuel cell shown in
FIG. 17.
[0067] FIG. 21 is a cross-sectional view schematically showing a
schematic configuration of the cathode separator of the fuel cell
according to Embodiment 6 of the present invention.
[0068] FIG. 22 is a cross-sectional view schematically showing a
schematic configuration of the cathode separator of the fuel cell
according to Embodiment 7 of the present invention.
[0069] FIG. 23 is a cross-sectional view schematically showing a
schematic configuration of the cathode separator of the fuel cell
according to Embodiment 8 of the present invention.
[0070] FIG. 24 is a cross-sectional view schematically showing a
schematic configuration of the fuel cell according to Embodiment 9
of the present invention.
[0071] FIG. 25 is a schematic diagram showing a schematic
configuration of the anode separator of the fuel cell shown in FIG.
24.
[0072] FIG. 26 is a cross-sectional view schematically showing a
schematic configuration of the fuel cell according to Embodiment 10
of the present invention.
[0073] FIG. 27 is a cross-sectional view schematically showing a
schematic configuration of the fuel cell according to Embodiment 11
of the present invention.
[0074] FIG. 28 is a schematic diagram showing a schematic
configuration of the anode separator of the fuel cell according to
Embodiment 12 of the present invention.
[0075] FIG. 29 is a schematic diagram showing a schematic
configuration of the cathode separator of the fuel cell according
to Embodiment 12 of the present invention.
[0076] FIG. 30 is a schematic diagram of a schematic configuration
of the anode separator of the fuel cell according to Embodiment 13
of the present invention.
[0077] FIG. 31 is a schematic diagram showing a schematic
configuration of the cathode separator of the fuel cell according
to Embodiment 13 of the present invention.
[0078] FIG. 32 is a schematic diagram showing a schematic
configuration of the anode separator of the fuel cell according to
Embodiment 14 of the present invention.
[0079] FIG. 33 is a schematic diagram showing a schematic
configuration of the cathode separator of the fuel cell according
to Embodiment 14 of the present invention.
[0080] FIG. 34 is a schematic diagram showing a schematic
configuration of the anode separator of the fuel cell according to
Embodiment 15 of the present invention.
[0081] FIG. 35 is a schematic diagram showing a schematic
configuration of the cathode separator of the fuel cell according
to Embodiment 15 of the present invention.
EXPLANATION OF REFERENCE NUMBERS
[0082] 1 polymer electrolyte membrane [0083] 2 anode catalyst layer
[0084] 3 anode gas diffusion layer [0085] 4 anode (gas diffusion
electrode) [0086] 4A portion [0087] 4B portion [0088] 4C uppermost
stream portion (uppermost stream portion of separator) [0089] 6
cathode catalyst layer [0090] 7 cathode gas diffusion layer [0091]
8 cathode (gas diffusion electrode) [0092] 8A portion [0093] 8B
portion [0094] 8C uppermost stream portion (uppermost stream
portion of separator) [0095] 10 membrane-electrode assembly
(polymer electrolyte layer-electrode assembly) [0096] 20 anode
separator (second separator) [0097] 21 fuel gas supplying manifold
hole [0098] 22 fuel gas discharging manifold hole [0099] 23
oxidizing gas supplying manifold hole [0100] 24 oxidizing gas
discharging manifold hole [0101] 25 cooling fluid supplying
manifold hole [0102] 26 cooling fluid discharging manifold hole
[0103] 27 fuel gas channel (second reactant gas channel) [0104] 27A
upstream portion (of fuel gas channel) [0105] 27B downstream
portion (of fuel gas channel) [0106] 27C uppermost stream portion
[0107] 27D downstream portion (remaining portion) [0108] 27E
portion [0109] 28, 38 cooling fluid channel [0110] 29, 39 rib
portion [0111] 29A rib portion (of upstream portion of fuel gas
channel) [0112] 29B rib portion (of downstream portion of fuel gas
channel) [0113] 30 cathode separator (first separator) [0114] 31
fuel gas supplying manifold hole (second reactant gas supplying
manifold hole) [0115] 32 fuel gas discharging manifold hole [0116]
33 oxidizing gas supplying manifold hole (first reactant gas
supplying manifold hole) [0117] 34 oxidizing gas discharging
manifold hole [0118] 35 cooling fluid supplying manifold hole
[0119] 36 cooling fluid discharging manifold hole [0120] 37
oxidizing gas channel (first reactant gas channel) [0121] 37A
upstream portion (of oxidizing gas channel) [0122] 37B downstream
portion (of oxidizing gas channel) [0123] 37C uppermost stream
portion [0124] 37D downstream portion (remaining portion) [0125]
37E portion [0126] 39A rib portion (of upstream portion of
oxidizing gas channel) [0127] 39B rib portion (of downstream
portion of oxidizing gas channel) [0128] 40, 41 gasket [0129] 51
meeting portion [0130] 52 projection [0131] 61 fuel cell stack
[0132] 62 cell stack body [0133] 63 first end plate [0134] 64
second end plate [0135] 71 central axis [0136] 100, 101 fuel cell
[0137] 127A reciprocating portion [0138] 127B inverting portion
[0139] 131 fuel gas supplying manifold [0140] 132 fuel gas
discharging manifold [0141] 133 oxidizing gas supplying manifold
[0142] 134 oxidizing gas discharging manifold [0143] 135 cooling
fluid supplying manifold [0144] 136 cooling fluid discharging
manifold [0145] 137A reciprocating portion [0146] 137B inverting
portion [0147] 137C horizontal portion [0148] 137D vertical portion
[0149] 202 electrode [0150] 202A portion [0151] 202B portion [0152]
203 reactant gas channel [0153] 204 rib portion [0154] D.sub.1
overall flow direction of oxidizing gas [0155] D.sub.2, D.sub.4
overall flow direction of cooling fluid [0156] D.sub.3 overall flow
direction of fuel gas
BEST MODE FOR CARRYING OUT THE INVENTION
[0157] Hereinafter, embodiments of the present invention will be
explained in reference to the drawings. In the drawings, the same
reference numbers are used for the same or corresponding portions,
and a repetition of the same explanation may be avoided.
Embodiment 1
[0158] FIG. 1 is a partial cross-sectional view showing the
configuration of a polymer electrolyte fuel cell (hereinafter
referred to as "fuel cell") of Embodiment 1 of the present
invention. FIG. 2 are diagrams showing the configurations of both
main surfaces of a cathode separator used in the fuel cell of FIG.
1. FIG. 2(a) is a plan view showing the main surface on which an
oxidizing gas channel is formed. FIG. 2(b) is a plan view showing
the main surface on which a cooling fluid channel is formed. FIG. 3
are diagrams showing the configurations of both main surfaces of an
anode separator used in the fuel cell of FIG. 1. FIG. 3(a) is a
plan view showing the main surface on which a fuel gas channel is
formed. FIG. 3(b) is a plan view showing the main surface on which
a cooling fluid channel is formed. In FIG. 1, the cooling fluid
channel is not shown. Hereinafter, the fuel cell of the present
embodiment will be explained in reference to FIGS. 1 to 3.
[0159] As shown in FIG. 1, a fuel cell 100 of the present
embodiment includes: a membrane-electrode assembly 10; a cathode
separator 30 and an anode separator 20 disposed to sandwich the
membrane-electrode assembly 10; and gaskets 40 and 41.
[0160] The membrane-electrode assembly 10 includes: a polymer
electrolyte membrane 1; an anode catalyst layer 2 and a cathode
catalyst layer 6 respectively disposed on both sides of the polymer
electrolyte membrane 1; an anode gas diffusion layer 3 disposed on
a main surface of the anode catalyst layer 2 which surface is
opposite a main surface located on the polymer electrolyte membrane
1 side; and a cathode gas diffusion layer 7 disposed on a main
surface of the cathode catalyst layer 6 which surface is opposite a
main surface located on the polymer electrolyte membrane 1
side.
[0161] The polymer electrolyte membrane 1 is formed as a
rectangular membrane piece. The polymer electrolyte membrane 1 has
proton conductivity. It is preferable that the polymer electrolyte
membrane 1 contain a sulfonic acid group, a carboxylic acid group,
a phosphonic acid group, or a sulfonimide group as a positive ion
exchange group. In light of the proton conductivity, it is more
preferable that the polymer electrolyte membrane 1 contain the
sulfonic acid group. It is especially preferable that the polymer
electrolyte membrane 1 be a membrane containing, as polymer
electrolyte that is a constituent material, a perfluoro carbon
copolymer containing a repeating unit based on a perfluorovinyl
compound expressed by
CF.sub.2.dbd.CF--(OCF.sub.2CFX).sub.m--O.sub.p--(CF.sub.2).sub.n--SO.sub.-
3H (m is an integer from 0 to 3, n is an integer from 1 to 12, p is
0 or 1, and X is a fluorine atom or a trifluoromethyl group) and a
repeating unit based on tetrafluoroethylene expressed by
CF.sub.2.dbd.CF.sub.2.
[0162] The anode catalyst layer 2 and the cathode catalyst layer 6
are respectively disposed on both main surfaces of the polymer
electrolyte membrane 1 so as to be opposed to each other. Each of
the anode catalyst layer 2 and the cathode catalyst layer 6 may be
configured to contain electrically-conductive carbon particles
supporting electrode catalyst and a polymer electrolyte having
positive ion (hydrogen ion) conductivity, or may be configured to
further contain a water-repellent material, such as
polytetrafluoroethylene. Specifically, as the polymer electrolyte,
materials described above as the constituent material of the
polymer electrolyte membrane 1 can be used. The polymer electrolyte
may be the same as or different from the above-described
constituent material of the polymer electrolyte membrane 1. The
electrode catalyst is constituted by metallic particles (for
example, metallic particles made of a precious metal), and is used
by being supported by the electrically-conductive carbon particles
(powder). The metallic particle is not especially limited, and
various metals can be used. However, in light of an electrode
reaction activity, it is preferable that the metallic particle be
at least one metal selected from the group consisting of platinum,
gold, silver, ruthenium, rhodium, palladium, osmium, iridium,
chromium, iron, titanium, manganese, cobalt, nickel, molybdenum,
tungsten, aluminum, silicon, zinc, and tin. Among these, platinum
or an alloy of platinum is preferable, and an alloy of platinum and
ruthenium is especially preferable since the activity of the
catalyst becomes stable in the anode.
[0163] The anode gas diffusion layer 3 is disposed on a main
surface of the anode catalyst layer 2 which surface is farther from
the polymer electrolyte membrane 1. The cathode gas diffusion layer
7 is disposed on a main surface of the cathode catalyst layer 6
which surface is farther from the polymer electrolyte membrane 1.
Each of the anode gas diffusion layer 3 and the cathode gas
diffusion layer 7 is constituted by carbon woven fabric, carbon
nonwoven fabric, carbon paper, carbon powder sheet, or the like.
The anode catalyst layer 2 and the anode gas diffusion layer 3 are
stacked on each other to form a flat plate shaped gas diffusion
electrode (anode) 4. Moreover, the cathode catalyst layer 6 and the
cathode gas diffusion layer 7 are stacked on each other to form a
flat plate shaped gas diffusion electrode (cathode) 8. The anode 4
and the cathode 8 are disposed to sandwich the polymer electrolyte
membrane 1 and be opposed to each other.
[0164] Next, the configuration of the cathode separator 30 will be
explained in reference to FIG. 2.
[0165] As shown in FIGS. 2(a) and 2(b), the cathode separator 30 is
formed to have a rectangular plate shape. An oxidizing gas
supplying manifold hole 33, an oxidizing gas discharging manifold
hole 34, a fuel gas supplying manifold hole 31, a fuel gas
discharging manifold hole 32, a cooling fluid supplying manifold
hole 35, and a cooling fluid discharging manifold hole 36 are
formed at a peripheral portion of the cathode separator 30. As
shown in FIG. 2(a), a groove-like oxidizing gas channel 37 for
exposing the cathode 8 to an oxidizing gas is formed on one of main
surfaces of the cathode separator 30. The oxidizing gas channel 37
is formed to connect the oxidizing gas supplying manifold hole 33
and the oxidizing gas discharging manifold hole 34. The oxidizing
gas channel 37 is formed to have a serpentine shape.
[0166] Here, a portion sandwiched by the oxidizing gas channel 37
of the cathode separator 30 is defined as a rib portion 39. This
definition is also applied to below-described Comparative Example,
Modification Examples, and Embodiments. Moreover, in the present
embodiment, the oxidizing gas channel 37 is constituted by an
upstream portion 37A and a downstream portion 37B. The upstream
portion 37A has an upstream end connected to the oxidizing gas
supplying manifold hole 33, and the downstream portion 37B is a
portion provided downstream of the upstream portion 37A and has a
downstream end connected to the oxidizing gas discharging manifold
hole 34.
[0167] The oxidizing gas channel 37 includes a plurality of
portions extending in parallel with one another. To be specific,
the oxidizing gas channel 37 is constituted by long channels (major
portions) linearly extending in a horizontal direction and short
channels linearly extending in a vertical direction, and the long
channels constitute the plurality of portions extending in parallel
with one another, and the short channels constitute the plurality
of portions extending in parallel with one another. In the
oxidizing gas channel 37, the area per unit area of a rib portion
39A formed by the upstream portion 37A is larger than the area per
unit area of a rib portion 39B formed by the downstream portion
37B. In other words, as shown in FIG. 1, a ratio W.sub.1/X.sub.1
that is a ratio of a width W.sub.1 of the rib portion 39A formed by
the upstream portion 37A to a width X.sub.1 of the oxidizing gas
channel 37 is higher than a ratio W.sub.2/X.sub.1 that is a ratio
of a width W.sub.2 of the rib portion 39B formed by the downstream
portion 37B to a width X.sub.2 of the oxidizing gas channel 37. In
the present embodiment, the width X.sub.1 of the oxidizing gas
channel 37 in the upstream portion 37A and the width X.sub.2 of the
oxidizing gas channel 37 in the downstream portion 37B are
substantially the same as each other. Moreover, in the present
embodiment, the upstream portion 37A and downstream portion 37B of
the oxidizing gas channel 37 are divided at a position of about 50%
of the entire length of the oxidizing gas channel 37. The upstream
portion 37A and the downstream portion 37B may be divided at a
position of 30% to 70% of the entire length of the oxidizing gas
channel 37. Here, the position at which the upstream portion 37A
and the downstream portion 37B are divided is determined in
accordance with the heat conductivity of the cathode separator 30,
the flow velocity of the oxidizing gas, the operating temperature
of the fuel cell 100, the degree of humidification in the oxidizing
gas, and the like.
[0168] As shown in FIG. 2(b), a groove-like cooling fluid channel
38 is formed on the other main surface of the cathode separator 30.
The cooling fluid channel 38 is formed to connect the cooling fluid
supplying manifold hole 35 and the cooling fluid discharging
manifold hole 36. The cooling fluid channel 38 is formed to have a
serpentine shape. The cooling fluid channel 38 is constituted by
long channels (major portions) linearly extending in the horizontal
direction and short channels linearly extending in the vertical
direction. The cooling fluid channel 38 and the oxidizing gas
channel 37 formed on the opposite surface are formed such that the
major portions thereof extend substantially in parallel with each
other. To be specific, the major portions of the cooling fluid
channel 38 are formed to extend substantially in parallel with the
major portions of the oxidizing gas channel 37 formed on the
opposite surface.
[0169] Moreover, as shown in FIGS. 2(a) and 2(b), the oxidizing gas
channel 37 and the cooling fluid channel 38 are formed such that an
overall flow direction D.sub.1 of the oxidizing gas flowing from
upstream to downstream in the oxidizing gas channel 37 and an
overall flow direction D.sub.2 of the cooling fluid flowing from
upstream to downstream in the cooling fluid channel 38 formed on
the opposite surface substantially coincide with each other. In
other words, the overall flow direction D.sub.1 of the oxidizing
gas flowing from upstream to downstream in the oxidizing gas
channel 37 and the overall flow direction D.sub.2 of the cooling
fluid flowing from upstream to downstream in the cooling fluid
channel 38 formed on the opposite surface form parallel flow.
[0170] The cathode separator 30 configured as above is disposed
such that the main surface on which the oxidizing gas channel 37 is
formed contacts the cathode 8.
[0171] Next, the configuration of the anode separator 20 will be
explained.
[0172] As shown in FIGS. 3(a) and 3(b), the anode separator 20 is
formed to have a rectangular plate shape. An oxidizing gas
supplying manifold hole 23, an oxidizing gas discharging manifold
hole 24, a fuel gas supplying manifold hole 21, a fuel gas
discharging manifold hole 22, a cooling fluid supplying manifold
hole 25, and a cooling fluid discharging manifold hole 26 are
formed at a peripheral portion of the anode separator 20. As shown
in FIG. 3(a), a groove-like fuel gas channel 27 for exposing the
anode 4 to a fuel gas is formed on one of main surfaces of the
anode separator 20. The fuel gas channel 27 is formed to connect
the fuel gas supplying manifold hole 21 and the fuel gas
discharging manifold hole 22. The fuel gas channel 27 is formed to
have a serpentine shape.
[0173] Here, a portion sandwiched by the fuel gas channel 27 of the
anode separator 20 is defined as a rib portion 29. This definition
is also applied to below-described Comparative Example,
Modification Examples, and Embodiments.
[0174] The fuel gas channel 27 includes a plurality of portions
extending in parallel with one another. The fuel gas channel 27 is
constituted by long channels (major portions) linearly extending in
the horizontal direction and short channels linearly extending in
the vertical direction. The fuel gas channel 27 is formed such that
intervals between the long channels linearly extending in the
horizontal direction are substantially the same as one another. In
other words, the widths of the rib portions 29 each sandwiched by
the fuel gas channel 27 are substantially the same as one another
in the entire region of the fuel gas channel 27.
[0175] As shown in FIG. 3(b), a groove-like cooling fluid channel
28 is formed on the other main surface of the anode separator 20.
The cooling fluid channel 28 is formed to connect the cooling fluid
supplying manifold hole 25 and the cooling fluid discharging
manifold hole 26. The cooling fluid channel 28 is formed to have a
serpentine shape. The cooling fluid channel 28 is constituted by
long channels (major portions) linearly extending in the horizontal
direction and short channels linearly extending in the vertical
direction.
[0176] The cooling fluid channel 28 and the fuel gas channel 27
formed on the opposite surface are formed such that the major
portions thereof extend substantially in parallel with each other.
To be specific, the major portions of the cooling fluid channel 28
are formed to extend substantially in parallel with the major
portions of the fuel gas channel 27 formed on the opposite
surface.
[0177] Moreover, as shown in FIGS. 3(a) and 3(b), the fuel gas
channel 27 and the cooling fluid channel 28 are formed such that an
overall flow direction D.sub.3 of the fuel gas flowing from
upstream to downstream in the fuel gas channel 27 and an overall
flow direction D.sub.4 of the cooling fluid flowing from upstream
to downstream in the cooling fluid channel 28 formed on the
opposite surface substantially coincide with each other. In other
words, the overall flow direction D.sub.3 of the fuel gas flowing
from upstream to downstream in the fuel gas channel 27 and the
overall flow direction D.sub.4 of the cooling fluid flowing from
upstream to downstream in the cooling fluid channel 28 formed on
the opposite surface form parallel flow.
[0178] The anode separator 20 configured as above is disposed such
that the main surface on which the fuel gas channel 27 is formed
contacts the anode 4.
[0179] Each of the gaskets 40 and 41 is formed to have a
rectangular ring shape. The gasket 40 is disposed to be located
around the membrane-electrode assembly 10 and between the anode
separator 20 and the polymer electrolyte membrane 1 of the
membrane-electrode assembly 10. The gasket 41 is disposed to be
located around the membrane-electrode assembly 10 and between the
cathode separator 30 and the polymer electrolyte membrane 1 of the
membrane-electrode assembly 10. The gaskets 40 and 41 are formed by
an adhesive using fluorocarbon rubber, silicon rubber, natural
rubber, ethylene-propylene rubber (EPDM), butyl rubber,
butylchloride rubber, butylbromide rubber, butadiene rubber,
styrene-butadiene copolymer, ethylene-vinyl acetate rubber, acryl
rubber, polyisopropylene polymer, perfluoro carbon, thermoplastic
elastomer (polystyrene-based elastomer, polyolefin-based elastomer,
polyester-based elastomer, polyamide-based elastomer, or the like),
or latex (isoprene rubber, butadiene rubber, or the like), a liquid
adhesive (adhesive using polybutadiene, polyisoprene,
polychloroprene, silicon rubber, fluorocarbon rubber,
acrylonitrile-butadiene rubber, or the like), or the like.
[0180] Next, operations of the fuel cell 100 configured as above
will be explained.
[0181] In FIGS. 1 to 3, in the fuel cell 100, the fuel gas is
supplied to a fuel gas supplying manifold (not shown) formed by
suitably connecting the fuel gas supplying manifold holes 21 and
31. The fuel gas flows through the fuel gas channels 27 of
respective cells. Meanwhile, the oxidizing gas is supplied to an
oxidizing gas supplying manifold (not shown) formed by suitably
connecting the oxidizing gas supplying manifold holes 23 and 33.
The oxidizing gas flows through the oxidizing gas channels 37 of
respective cells. Moreover, cooling water is supplied to a cooling
water supplying manifold (not shown) formed by suitably connecting
the cooling water supplying manifold holes 25 and 35. The cooling
water flows through the cooling fluid channels 28 and 38 of
respective cells. Then, the fuel gas and the oxidizing gas react
with each other in the anode and cathode of the membrane-electrode
assembly 10 to generate electricity and heat. The generated
electricity is output to outside through the anode separator 20 and
the cathode separator 30. The unreacted (unconsumed) fuel gas is
discharged to outside through a fuel gas discharging manifold (not
shown) formed by suitably connecting the fuel gas discharging
manifold holes 22 and 32. Moreover, the unreacted (unconsumed)
oxidizing gas is discharged to outside through a fuel gas
discharging manifold (not shown) formed by suitably connecting the
oxidizing gas discharging manifold holes 24 and 34. Meanwhile, the
generated heat is recovered by the cooling water flowing through
the cooling fluid channels 28 and 38. The cooling water having
recovered the heat is discharged to outside through a cooling water
discharging manifold (not shown) formed by suitably connecting the
cooling water discharging manifold holes 26 and 36.
[0182] Next, operational advantages of the present invention will
be explained in detail while being compared with Comparative
Example to clarify the superiority of the present invention.
[0183] FIG. 4 is a partial cross-sectional view showing the
configuration of the fuel cell of Comparative Example. FIG. 5 are
diagrams showing the configurations of both main surfaces of the
cathode separator used in the fuel cell of FIG. 4. FIG. 5(a) is a
plan view showing the main surface on which the cathode gas channel
is formed. FIG. 5(b) is a plan view showing the main surface on
which the cooling fluid channel is formed. In FIG. 4, the cooling
fluid channel is not shown. Hereinafter, the fuel cell of
Comparative Example will be explained in reference to FIGS. 4 and
5.
[0184] As shown in FIGS. 4 and 5, the configuration of the cathode
separator 30 used in a fuel cell 101 of Comparative Example is
different from the configuration of the cathode separator 30 used
in the fuel cell 100 of Embodiment 1.
[0185] To be specific, in the oxidizing gas channel 37 of the
cathode separator 30 used in the fuel cell 101 of Comparative
Example, the widths of the portions each located between the
channels (major portions) linearly extending in the horizontal
direction are substantially the same as one another. In other
words, the widths of the rib portions 39 each sandwiched by the
oxidizing gas channel 37 are substantially the same as one another
in the entire region of the oxidizing gas channel 37. The other
configuration of the fuel cell 101 of Comparative Example is the
same as the configuration of the fuel cell 100 of Embodiment 1.
[0186] Next, the fuel cell 100 of Embodiment 1 and the fuel cell
101 of Comparative Example are compared with each other.
[0187] FIG. 6 are diagrams showing temperature distributions of
respective portions of the fuel cell. FIG. 6(a) shows the
temperature distributions of respective portions in the cross
section of the fuel cell of Embodiment 1. FIG. 6(b) shows the
temperature distributions of respective portions in the cross
section of the fuel cell of Comparative Example. In FIGS. 6(a) and
6(b), a horizontal axis denotes respective portions, and a vertical
axis denotes temperatures. The fuel cell of Embodiment 1 and the
fuel cell of Comparative Example are compared with each other in
reference to FIG. 6 to clarify the advantages of the fuel cell of
the present embodiment.
[0188] As shown in FIG. 6(a), in the upstream portion 37A of the
oxidizing gas channel 37 of the fuel cell 100 of Embodiment 1, the
temperature of the main surface of the cathode catalyst layer 6
which surface is located on the cathode gas diffusion layer 7 side
(the main surface of the cathode gas diffusion layer 7 which
surface is located on the cathode catalyst layer 6 side) is a
temperature T.sub.1. The temperature of the main surface of the
cathode gas diffusion layer 7 which surface is located on the
cathode separator 30 side (the main surface of the cathode
separator 30 which surface is located on the cathode gas diffusion
layer 7 side) is a temperature T.sub.1. The temperature of the main
surface of the cathode separator 30 which surface is opposite the
main surface located on the cathode gas diffusion layer 7 side is a
temperature T.sub.3. To be specific, the temperature decreases and
the gradient of temperature decrease becomes higher in a thickness
direction of the cell from the center (polymer electrolyte membrane
1) of the cell to outside of the cell, i.e., to the cathode
catalyst layer 6, the cathode gas diffusion layer 7, and the
cathode separator 30.
[0189] Meanwhile, in the downstream portion 37B of the oxidizing
gas channel 37, the temperature of the main surface of the cathode
catalyst layer 6 which surface is located on the cathode gas
diffusion layer 7 side (the main surface of the cathode gas
diffusion layer 7 which surface is located on the cathode catalyst
layer 6 side) is the temperature T.sub.1. The temperature of the
main surface of the cathode gas diffusion layer 7 which surface is
located on the cathode separator 30 side (the main surface of the
cathode separator 30 which surface is located on the cathode gas
diffusion layer 7 side) is a temperature (T.sub.1') between the
temperatures T.sub.1 and T.sub.2. The temperature of the main
surface of the cathode separator 30 which surface is opposite the
main surface located on the cathode gas diffusion layer 7 side is
the temperature T.sub.3. To be specific, the temperature decreases
in the thickness direction of the cell from the center (polymer
electrolyte membrane 1) of the cell to outside of the cell, i.e.,
to the cathode catalyst layer 6, the cathode gas diffusion layer 7,
and the cathode separator 30, and the gradient of temperature
decrease of the downstream portion 37B is lower than the gradient
of temperature decrease of the upstream portion 37A.
[0190] Meanwhile, as shown in FIG. 6(b), in the fuel cell 101 of
Comparative Example, the temperature of the main surface of the
cathode catalyst layer 6 which surface is located on the cathode
gas diffusion layer 7 side (the main surface of the cathode gas
diffusion layer 7 which surface is located on the cathode catalyst
layer 6 side) is the temperature T.sub.1. The temperature of the
main surface of the cathode gas diffusion layer 7 which surface is
located on the cathode separator 30 side (the main surface of the
cathode separator 30 which surface is located on the cathode gas
diffusion layer 7 side) is the temperature T.sub.2. The temperature
of the main surface of the cathode separator 30 which surface is
opposite the main surface located on the cathode gas diffusion
layer 7 side is the temperature T.sub.3. To be specific, in the
entire flow region of the fuel cell 101 of Comparative Example, the
temperature decreases and the gradient of temperature decrease
becomes higher in the thickness direction of the cell from the
center (polymer electrolyte membrane 1) of the cell to outside of
the cell, i.e., to the cathode catalyst layer 6, the cathode gas
diffusion layer 7, and the cathode separator 30, as with the
upstream portion 37A of the fuel cell 100 of Embodiment 1.
[0191] In accordance with the above, the temperature of the cathode
gas diffusion layer 7 corresponding to the downstream portion 37B
in the fuel cell 100 of Embodiment 1 is higher than the temperature
of the entire flow region of the fuel cell 101 of Comparative
Example.
[0192] As above, in the fuel cell 100 of the present embodiment, a
contact area between the rib portion 39B formed by the downstream
portion 37B of the oxidizing gas channel 37 and the cathode gas
diffusion layer 7 is smaller than that in Comparative Example.
Therefore, the amount of heat transferred from the cathode catalyst
layer 6 to the cathode separator 30 is small, and the temperature
of the cathode gas diffusion layer 7 corresponding to the
downstream portion 37B of the oxidizing gas channel 37 becomes
high. With this, the dew condensation of the water generated by the
electric power generating reaction is less likely to occur, and the
occurrence of the flooding is suppressed in not only the oxidizing
gas channel 37 but also the cathode gas diffusion layer 7.
[0193] Meanwhile, in the upstream portion 37A of the oxidizing gas
channel 37, current concentration may occur since the amount of the
reactant gas related to a battery reaction is large, and a battery
voltage may decrease due to the increase in a contact resistance.
However, as in the fuel cell 100 of the present embodiment, by
increasing the contact area between the rib portion 39A and the
cathode 8 in the upstream portion 37A of the oxidizing gas channel
37, the contact resistance is reduced, and the decrease in the
battery voltage is suppressed.
[0194] Moreover, in the fuel cell 100 of the present embodiment,
the cooling fluid channels 28 and 38, the fuel gas channel 27, and
the oxidizing gas channel 37 are formed such that the major
portions thereof are substantially in parallel with one another.
Further, in the fuel cell 100 of the present embodiment, the
cooling fluid channels 38 and 28, the oxidizing gas channel 37, and
the fuel gas channel 27 are formed such that the cooling fluid and
the oxidizing gas forms the parallel flow and the cooling fluid and
the fuel gas forms the parallel flow. Therefore, the cooling fluid
which has not yet recovered the heat and is low in temperature
flows through the cooling fluid channel 38 formed on the surface
opposite the surface on which the upstream portion 37A where the
electric power generation concentrates is located, so that a
cooling efficiency improves. In contrast, the cooling fluid which
has recovered the heat and is high in temperature flows through the
cooling fluid channel 38 formed on the surface opposite the surface
on which the downstream portion 37B of the oxidizing gas channel 37
is located, so that the temperature of the downstream portion 37B
increases. With this, in the downstream portion 37B of the
oxidizing gas channel 37, the dew condensation of the generated
water is even less likely to occur, and the occurrence of the
flooding is further suppressed.
[0195] In the cathode separator 30 of the fuel cell 100 of the
present invention, since the oxidizing gas channel 37 is large in
length, the resistance in the channel is high. Therefore, if the
configuration of the channel groove is the same between the
upstream portion 37A and the downstream portion 37B, the pressure
loss increases, and the flow rate decreases. On this account, it is
preferable that the oxidizing gas channel 37 be formed such that
the pressure loss does not change between the upstream portion 37A
and the downstream portion 37B by forming a deeper channel groove
of the downstream portion 37B of the oxidizing gas channel 37,
forming the downstream portion 37B by a plurality of channel
grooves, or changing the ratio of the rib portions between the
upstream portion 37A and the downstream portion 37B.
Modification Example 1
[0196] FIG. 7 is a partial cross-sectional view showing
Modification Example 1 of the fuel cell of Embodiment 1. FIG. 8 are
diagrams showing the configurations of both main surfaces of the
anode separator used in the fuel cell of FIG. 7. FIG. 8(a) is a
plan view showing the main surface on which the fuel gas channel is
formed. FIG. 8(b) is a plan view showing the main surface on which
the cooling fluid channel is formed. In FIG. 7, the cooling fluid
channel is not shown. Hereinafter, the fuel cell of Modification
Example 1 will be explained in reference to FIGS. 7 and 8.
[0197] The configuration of the anode separator 20 in the fuel cell
100 of Modification Example 1 is different from the configuration
of the anode separator 20 in the fuel cell of Embodiment 1. To be
specific, as shown in FIGS. 7 and 8, in Modification Example 1, the
fuel gas channel 27 is constituted by an upstream portion 27A and a
downstream portion 27B. The upstream portion 27A has an upstream
end connected to the fuel gas supplying manifold hole 21, and the
downstream portion 27B is a portion provided downstream of the
upstream portion 27A and has a downstream end connected to the fuel
gas discharging manifold hole 22.
[0198] The fuel gas channel 27 includes a plurality of portions
extending in parallel with one another. To be specific, the fuel
gas channel 27 is constituted by long channels (major portions)
linearly extending in the horizontal direction and short channels
linearly extending in the vertical direction, and the long channels
constitute the plurality of portions extending in parallel with one
another, and the short channels constitute the plurality of
portions extending in parallel with one another. In the fuel gas
channel 27, the area per unit area of a rib portion 29A formed by
the upstream portion 27A is larger than the area per unit area of a
rib portion 29B formed by the downstream portion 27B. In other
words, as shown in FIG. 7, a ratio W.sub.1/Y.sub.1 that is a ratio
of the width W.sub.1 of the rib portion 29A formed by the upstream
portion 27A to a width Y.sub.1 of the fuel gas channel 27 is higher
than a ratio W.sub.2/Y.sub.2 that is a ratio of the width W.sub.2
of the rib portion 29B formed by the downstream portion 27B to a
width Y.sub.2 of the fuel gas channel 27. In the present
embodiment, the width Y.sub.1 of the fuel gas channel 27 in the
upstream portion 27A and the width Y.sub.2 of the fuel gas channel
27 in the downstream portion 27B are substantially the same as each
other. Moreover, in the present embodiment, the upstream portion
27A and the downstream portion 27B are divided at a position of
about 50% of the entire length of the fuel gas channel 27. The
upstream portion 27A and the downstream portion 27B may be divided
at a position of 30% to 70% of the entire length of the fuel gas
channel 27. Here, the position at which the upstream portion 27A
and the downstream portion 27B are divided is determined in
accordance with the heat conductivity of the anode separator 20,
the flow velocity of the fuel gas, the operating temperature of the
fuel cell 100, the degree of humidification in the fuel gas, and
the like. The other configuration of the fuel cell 100 of
Modification Example 1 is the same as the configuration of the fuel
cell 100 of Embodiment 1.
[0199] With this configuration, in the fuel cell 100 of Embodiment
1, the fuel gas channel 27 can obtain the same effects as the
oxidizing gas channel 37.
[0200] Moreover, a contact area between the rib portion 29B formed
by the downstream portion 27B of the fuel gas channel 27 and the
anode gas diffusion layer 3 is smaller than that in Comparative
Example. Therefore, the amount of heat transferred from the anode
catalyst layer 2 to the anode separator 20 is small, and the
temperature of the anode gas diffusion layer 3 corresponding to the
downstream portion 27B of the fuel gas channel 27 becomes high.
With this, the dew condensation of the generated water (generated
water having diffused from the cathode 8 to the anode 4) generated
by the electric power generating reaction is less likely to occur,
and the occurrence of the flooding is suppressed in not only the
fuel gas channel 27 but also the anode gas diffusion layer 3.
[0201] Meanwhile, in the upstream portion 37A of the oxidizing gas
channel 37 and the upstream portion 27A of the fuel gas channel 27,
the current concentration may occur since the amount of the
reactant gas related to the battery reaction is large, and the
battery voltage may decrease due to the increase in the contact
resistance. However, as in the fuel cell 100 of Modification
Example 1, by increasing the contact area between the rib portion
39A and the cathode 8 in the upstream portion 37A of the oxidizing
gas channel 37 and increasing the contact area between the rib
portion 29A and the anode 4 in the upstream portion 27A of the fuel
gas channel 27, the contact resistance is further reduced, and the
decrease in the battery voltage is further suppressed.
Modification Example 2
[0202] FIG. 9 is a partial cross-sectional view showing
Modification Example 2 of the fuel cell of Embodiment 1. In FIG. 9,
the cooling fluid channel is not shown. Hereinafter, the fuel cell
of Modification Example 2 will be explained in reference to FIG.
9.
[0203] In the fuel cell 100 of Modification Example 2, the
separator shown in FIG. 5 is used as the cathode separator 30, and
the separator shown in FIG. 8 is used as the anode separator 20.
The other configuration of the fuel cell 100 of Modification
Example 2 is the same as the configuration of the fuel cell of
Modification Example 1.
[0204] With this configuration, the dew condensation of the
generated water (generated water having diffused from the cathode 8
to the anode 4) generated by the electric power generating reaction
is less likely to occur, and the occurrence of the flooding is
suppressed in not only the fuel gas channel 27 but also the anode
gas diffusion layer 3.
Embodiment 2
[0205] FIG. 10 is a partial cross-sectional view showing the
configuration of the fuel cell of Embodiment 2 of the present
invention. FIG. 11 are diagrams showing the configurations of both
main surfaces of the cathode separator used in the fuel cell of
FIG. 10. FIG. 11(a) is a plan view showing the main surface on
which the oxidizing gas channel is formed. FIG. 11(b) is a plan
view showing the main surface on which the cooling fluid channel is
formed. In FIG. 10, the cooling fluid channel is not shown.
Hereinafter, the fuel cell of the present embodiment will be
explained in reference to FIGS. 10 and 11.
[0206] The configuration of the cathode separator 30 used in the
fuel cell 100 of the present embodiment is different from that of
Embodiment 1. To be specific, as shown in FIG. 10, in the cathode
separator 30 constituting the fuel cell 100 of the present
embodiment, the channel groove of the downstream portion 37B of the
oxidizing gas channel 37 is formed such that a width thereof
becomes wider in a direction from a bottom thereof toward an
opening thereof, and a side wall thereof has a tapered shape. Thus,
as shown in FIG. 11, in the oxidizing gas channel 37, the area per
unit area of the rib portion 39A formed by the upstream portion 37A
is larger than the area per unit area of the rib portion 39B formed
by the downstream portion 37B. In other words, as shown in FIG. 10,
a ratio W.sub.3/X.sub.3 that is a ratio of a width W.sub.3 of the
rib portion 39A formed by the upstream portion 37A to a width
X.sub.3 of the oxidizing gas channel 37 is higher than a ratio
W.sub.4/X.sub.4 that is a ratio of a width W.sub.4 of the rib
portion 39B formed by the downstream portion 37B to a width X.sub.4
of the opening of the oxidizing gas channel 37. The other
configuration of the cathode separator 30 used in the fuel cell 100
of the present embodiment is the same as the configuration of the
cathode separator used in the fuel cell of Embodiment 1.
[0207] Even with this configuration, the contact area between the
rib portion 39B formed by the downstream portion 37B of the
oxidizing gas channel 37 and the cathode gas diffusion layer 7
becomes smaller than that in Comparative Example. Therefore, the
fuel cell of Embodiment 2 can obtain the same effects as the fuel
cell of Embodiment 1.
[0208] Moreover, since the width of the opening of the downstream
portion 37B of the oxidizing gas channel 37 is increased by forming
the tapered-shape side wall, the cross-sectional area of the
channel groove of the oxidizing gas channel 37 is not increased so
much (see FIG. 10), so that the flow velocity of the oxidizing gas
flowing through the oxidizing gas channel 37 does not decrease so
much. With this, the occurrence of the flooding due to the decrease
in the flow velocity can also be suppressed.
Embodiment 3
[0209] FIG. 12 is a partial cross-sectional view showing the
configuration of the fuel cell of Embodiment 3 of the present
invention. FIG. 13 are diagrams showing the configurations of both
main surfaces of the cathode separator used in the fuel cell of
FIG. 12. FIG. 13(a) is a plan view showing the main surface on
which the oxidizing gas channel is formed. FIG. 13(b) is a plan
view showing the main surface on which the cooling fluid channel is
formed. In FIG. 12, the cooling fluid channel is not shown.
Hereinafter, the fuel cell of the present embodiment will be
explained in reference to FIGS. 12 and 13.
[0210] The configuration of the cathode separator 30 used in the
fuel cell 100 of the present embodiment is different from that of
Embodiment 1. To be specific, as shown in FIG. 12, in the cathode
separator 30 constituting the fuel cell 100 of the present
embodiment, the channel groove of the downstream portion 37B of the
oxidizing gas channel 37 is formed such that a corner portion of an
opening edge of the side wall thereof is linearly chamfered (cut).
Thus, as shown in FIG. 13, in the oxidizing gas channel 37, the
area per unit area of the rib portion 39A formed by the upstream
portion 37A is larger than the area per unit area of the rib
portion 39B formed by the downstream portion 37B. In other words,
as shown in FIG. 12, a ratio W.sub.5/X.sub.5 that is a ratio of a
width Ws of the rib portion 39A formed by the upstream portion 37A
to a width X.sub.5 of the oxidizing gas channel 37 is higher than a
ratio W.sub.6/X.sub.6 that is a ratio of a width W.sub.6 of the rib
portion 39B formed by the downstream portion 37B to a width X.sub.6
of the opening of the oxidizing gas channel 37. The other
configuration of the cathode separator 30 used in the fuel cell 100
of the present embodiment is the same as the configuration of the
cathode separator used in the fuel cell of Embodiment 1.
[0211] Even with this configuration, the contact area between the
rib portion 39B formed by the downstream portion 37B of the
oxidizing gas channel 37 and the cathode gas diffusion layer 7
becomes smaller than that in Comparative Example. Therefore, the
fuel cell 100 of Embodiment 3 can obtain the same effects as the
fuel cell of Embodiment 1.
[0212] Moreover, since the width of the opening of the downstream
portion 37B of the oxidizing gas channel 37 is increased by
chamfering the corner portion of the opening edge of the side wall,
the cross-sectional area of the channel groove of the oxidizing gas
channel 37 is not increased so much (see FIG. 12), so that the flow
velocity of the oxidizing gas flowing through the oxidizing gas
channel 37 does not decrease so much. With this, the occurrence of
the flooding due to the decrease in the flow velocity can also be
suppressed.
Embodiment 4
[0213] FIG. 14 are diagrams showing the configurations of both main
surfaces of the cathode separator used in the fuel cell of
Embodiment 4 of the present invention. FIG. 14(a) is a plan view
showing the main surface on which the oxidizing gas channel is
formed. FIG. 14(b) is a plan view showing the main surface on which
the cooling fluid channel is formed. Hereinafter, the fuel cell of
the present embodiment will be explained in reference to FIG.
14.
[0214] The configuration of the cathode separator 30 used in the
fuel cell of the present embodiment is different from that in
Embodiment 1. To be specific, as shown in FIG. 14, in the fuel cell
of the present embodiment, the oxidizing gas channel 37 of the
cathode separator 30 is constituted by a plurality of channel
grooves. Herein, the number of channel grooves is three. Each of
the channel grooves is formed to connect the oxidizing gas
supplying manifold hole 33 and the oxidizing gas discharging
manifold hole 34. Then, a meeting portion 51 where the channel
grooves meet is formed at a portion of the oxidizing gas channel
37. The meeting portion 51 is formed at a connection portion where
the upstream portion 37A and downstream portion 37B of the
oxidizing gas channel 37 are connected to each other. In the
present embodiment, the upstream portion 37A and downstream portion
37B of the oxidizing gas channel 37 are divided at a position of
about 30% of the entire length of the oxidizing gas channel 37. The
upstream portion 37A and the downstream portion 37B may be divided
at a position of 30% to 70% of the entire length of the oxidizing
gas channel 37. Moreover, the number of channels provided
downstream of the meeting portion 51 may be reduced. The meeting
portion 51 is constituted by a substantially triangular recess and
a plurality of (six in the present embodiment) columnar projections
52 formed in the recess. The other configuration of the cathode
separator 30 used in the fuel cell of the present embodiment is the
same as the configuration of the cathode separator used in the fuel
cell of Embodiment 1.
[0215] Even with this configuration, the fuel cell of Embodiment 4
can obtain the same effects as the fuel cell of Embodiment 1.
Moreover, in the meeting portion 51, only the projections 52 and
the cathode gas diffusion layer 7 contact each other, so that the
contact area between the cathode separator 30 and the cathode gas
diffusion layer 7 becomes small. With this, the temperature
decrease is prevented at not only the downstream portion 37B of the
oxidizing gas channel 37 but also the meeting portion 51.
[0216] Further, with this configuration, after the oxidizing gas is
adequately mixed in the meeting portion 51, it flows from the
upstream portion 37A to the downstream portion 37B in the oxidizing
gas channel 37.
[0217] Needless to say, the fuel gas channel 27 of each of
Modification Examples 1 and 2 of Embodiment 1 may be configured in
the same manner as the oxidizing gas channel 37 of any one of
Embodiments 2 to 4. Moreover, needless to say, the fuel gas channel
27 of each of Embodiments 1 to 4 may be configured in the same
manner as the oxidizing gas channel 37 of any one of Embodiments 2
to 4.
[0218] Moreover, in the above embodiments, each of the oxidizing
gas channel 37 and the fuel gas channel 27 is formed to have a
serpentine shape or a serpentine shape including the meeting
portion 51. However, the shape of each of the oxidizing gas channel
37 and the fuel gas channel 27 is not limited to this. Each of the
oxidizing gas channel 37 and the fuel gas channel 27 may have any
shape as long as each of the rib portions 39 and 29 is formed by
being sandwiched between different portions of each of the
oxidizing gas channel 37 and the fuel gas channel 27. For example,
each of the oxidizing gas channel 37 and the fuel gas channel 27
may be constituted by a plurality of channel grooves extending in
parallel with one another, or may be configured such that a
plurality of minor channel grooves extending in parallel with one
another connect a pair of major channel grooves.
[0219] Further, in the embodiments and Modification Examples, the
oxidizing gas channel 37 is constituted by two portions that are
the upstream portion 37A and the downstream portion 37B, and the
fuel gas channel 27 is constituted by two portions that are the
upstream portion 27A and the downstream portion 27B. However, each
of the oxidizing gas channel 37 and the fuel gas channel 27 may
have a midstream portion having an area which is intermediate
between the area of the rib portion 39A, 29A per unit area of the
upstream portion 37A, 27A and the area of the rib portion 39B, 29B
per unit area of the downstream portion 37B, 27B. Moreover, the
area of each of the rib portions 39 and 29 per unit area may be
gradually changed (reduced) from the upstream portion 37A, 27A to
the downstream portion 37B, 27B.
Embodiment 5
Configuration of Fuel Cell Stack
[0220] FIG. 16 is a perspective view schematically showing a
schematic configuration of a fuel cell stack according to
Embodiment 5 of the present invention. In FIG. 16, a vertical
direction of the fuel cell stack is shown as a vertical direction
of the drawing.
[0221] As shown in FIG. 16, a fuel cell stack 61 according to
Embodiment 5 of the present invention includes a cell stack body
62, first and second end plates 63 and 64, and fastening members,
not shown. The cell stack body 62 is formed by stacking
plate-shaped polymer electrolyte fuel cells (hereinafter simply
referred to as "fuel cells") 100 in its thickness direction. The
first and second end plates 63 and 64 are respectively disposed on
both ends of the cell stack body 62. The fastening members fasten
the cell stack body 62 and the first and second end plates 63 and
64 in a stack direction of the fuel cells 100. Although not shown,
a current collector and an insulating plate are disposed on each of
the first and second end plates 63 and 64. The plate-shaped fuel
cell 100 extends in parallel with a vertical surface, and the stack
direction of the fuel cells 100 is a horizontal direction.
[0222] An oxidizing gas supplying manifold hole 133 is formed at an
upper portion of one side portion (side portion shown on the left
side in the drawing; hereinafter referred to as "first side
portion") of the cell stack body 62 so as to penetrate the cell
stack body 62 in the stack direction of the fuel cells 100 of the
cell stack body 62. A cooling fluid discharging manifold 136 is
formed below the oxidizing gas supplying manifold 133. Moreover, a
cooling fluid supplying manifold 135 is formed on an upper inner
side of the oxidizing gas supplying manifold 133 of the first side
portion of the cell stack body 62 so as to penetrate the cell stack
body 62 in the stack direction of the fuel cells 100 of the cell
stack body 62. Similarly, a fuel gas discharging manifold 132 is
formed on a lower inner side of the cooling fluid discharging
manifold 136 so as to penetrate the cell stack body 62 in the stack
direction of the fuel cells 100 of the cell stack body 62. Further,
a fuel gas supplying manifold 131 is formed at an upper portion of
the other side portion (side portion shown on the right side in the
drawing; hereinafter referred to as "second side portion") of the
cell stack body 62 so as to penetrate the cell stack body 62 in the
stack direction of the fuel cells 100 of the cell stack body 62. An
oxidizing gas discharging manifold 134 is formed below the fuel gas
supplying manifold 131 so as to penetrate the cell stack body 62 in
the stack direction of the fuel cells 100 of the cell stack body
62.
[0223] Then, suitable pipes are provided for respective manifolds.
With this, the fuel gas, the oxidizing gas, and the cooling fluid
are supplied to and discharged from the fuel cell stack 61 through
the suitable pipes.
[0224] Configuration of Polymer Electrolyte Fuel Cell
[0225] Next, the configuration of the polymer electrolyte fuel cell
according to Embodiment 5 of the present invention will be
explained in reference to FIG. 17.
[0226] FIG. 17 is a cross-sectional view schematically showing a
schematic configuration of the fuel cell 100 of the fuel cell stack
61 shown in FIG. 16. In FIG. 17, a part of the fuel cell 100 is
omitted.
[0227] As shown in FIG. 17, the polymer electrolyte fuel cell 100
according to Embodiment 5 includes the MEA (membrane-electrode
assembly) 10, the gaskets 40 and 41, the anode separator (second
separator) 20, and the cathode separator (first separator) 30.
[0228] The MEA 10 includes a polymer electrolyte membrane (for
example, Nafion (Product Name) produced by DuPont in the U.S.) 1
which selectively transports hydrogen ions, the anode 4, and the
cathode 8
[0229] The polymer electrolyte membrane 1 has a substantially
quadrangular (herein, rectangular) shape. The anode 4 and the
cathode 8 (each of which is referred to as "(gas diffusion)
electrode") are respectively disposed on both surfaces of the
polymer electrolyte membrane 1 so as to be located inwardly of a
peripheral portion of the polymer electrolyte membrane 1.
Below-described manifold holes (not shown), such as the fuel gas
supplying manifold hole, are formed at the peripheral portion of
the polymer electrolyte membrane 1 so as to penetrate the polymer
electrolyte membrane 1 in the thickness direction.
[0230] The anode 4 is disposed on one of main surfaces of the
polymer electrolyte membrane 1, and includes the anode catalyst
layer 2 and the anode gas diffusion layer 3. The anode catalyst
layer 2 is made of a mixture of electrically-conductive carbon
particles supporting electrode catalyst (for example, a precious
metal, such as platinum) and a polymer electrolyte having hydrogen
ion conductivity. The anode gas diffusion layer 3 is disposed on
one main surface of the anode catalyst layer 2, and has both gas
permeability and electrical conductivity. Similarly, the cathode 8
is disposed on the other main surface of the polymer electrolyte
membrane 1, and includes the cathode catalyst layer 6 and the
cathode gas diffusion layer 7. The cathode catalyst layer 6 is made
of a mixture of electrically-conductive carbon particles supporting
electrode catalyst (for example, a precious metal, such as
platinum) and a polymer electrolyte having hydrogen ion
conductivity. The cathode gas diffusion layer 7 is disposed on one
main surface of the cathode catalyst layer 6, and has both gas
permeability and electrical conductivity.
[0231] The anode catalyst layer 2 and the cathode catalyst layer 6
can be formed by a method known in the art using catalyst layer
forming ink containing electrically-conductive carbon particles
supporting electrode catalyst made of a precious metal, a polymer
electrolyte, and a dispersion medium. Moreover, a material
constituting the anode gas diffusion layer 3 and the cathode gas
diffusion layer 7 is not especially limited, and a material known
in the art can be used. For example, electrically-conductive porous
base materials, such as carbon cloth and carbon paper, can be used.
Moreover, the electrically-conductive porous base material may be
subjected to water repellent finish by a conventionally known
method.
[0232] Moreover, a pair of ring-shaped, substantially rectangular,
fluorocarbon-rubber gaskets 40 and 41 are respectively disposed
around the anode 4 and cathode 8 of the MEA 10 so as to sandwich
the polymer electrolyte membrane 1. With this, the leakage of the
fuel gas, air, and the oxidizing gas to outside of the cell is
suppressed, and the mixing of these gases in the fuel cell 100 is
suppressed. Below-described manifold holes (not shown), such as the
fuel gas supplying manifold hole, are formed at the peripheral
portions of the gaskets 40 and 41 so as to penetrate the gaskets 40
and 41 in the thickness direction.
[0233] Moreover, the electrically-conductive, plate-shaped anode
separator 20 and cathode separator 30 are disposed to sandwich the
MEA 10 and the gaskets 40 and 41. With this, the MEA 10 is
mechanically fixed. When a plurality of fuel cells 100 are stacked
in the thickness direction, the MEAs 10 are electrically connected
to one another. As the separators 20 and 30, a metal having
excellent heat conductivity and electrical conductivity, a
graphite, or a mixture of graphite and resin may be used. For
example, a separator produced by injection molding using a mixture
of carbon powder and binder (solvent) may be used, or a titanium
plate whose surface is subjected to gold plating or a stainless
steel plate whose surface is subjected to gold plating may be
used.
[0234] The groove-like fuel gas channel (second reactant gas
channel) 27 through which the fuel gas flows is formed on one main
surface (hereinafter referred to as "inner surface") of the anode
separator 20 which surface contacts the anode 4. Moreover, the
groove-like cooling fluid channel 28 through which the cooling
fluid flows is formed on the other main surface (hereinafter
referred to as "outer surface") of the anode separator 20.
Similarly, the groove-like oxidizing gas channel (first reactant
gas channel) 37 through which the oxidizing gas flows is formed on
one main surface (hereinafter referred to as "inner surface") of
the cathode separator 30 which surface contacts the cathode 8.
Moreover, the groove-like cooling fluid channel 38 through which
the cooling fluid flows is formed on the other main surface
(hereinafter referred to as "outer surface") of the cathode
separator 30.
[0235] With this, the fuel gas and the oxidizing gas are
respectively supplied to the anode 4 and the cathode 8, and these
gases react with each other to generate electricity and heat.
Moreover, the cooling fluid, such as the cooling water, is caused
to flow through the cooling fluid channels 28 and 38 to recover the
generated heat.
[0236] The fuel cell 100 configured as above may be used as a unit
cell (cell), or a plurality of fuel cells 100 may be used as the
fuel cell stack 61 by stacking the fuel cells 100. Moreover, in the
case of stacking the fuel cells 100, the cooling fluid channels 28
and 38 may be formed for every two or three unit cells. Further, in
the case of not forming the cooling fluid channels 28 and 38
between the unit cells, a separator which is sandwiched between two
MEAs 10 and in which the fuel gas channel 27 is formed on one main
surface thereof and the oxidizing gas channel 37 is formed on the
other main surface thereof may be used as a separator serving as
both the anode separator 20 and the cathode separator 30. Moreover,
herein, the first separator is the cathode separator 30, the second
separator is the anode separator 20, the first reactant gas channel
is the oxidizing gas channel 37, and the second reactant gas
channel is the fuel gas channel 27. However, the present embodiment
is not limited to this. The first separator may be the anode
separator 20, the second separator may be the cathode separator 30,
the first reactant gas channel may be the fuel gas channel 27, and
the second reactant gas channel may be the oxidizing gas channel
37.
[0237] Configuration of Separator
[0238] Next, the anode separator 20 and the cathode separator 30
will be explained in detail in reference to FIGS. 17 to 19.
[0239] FIG. 18 is a schematic diagram showing a schematic
configuration of the anode separator 20 of the fuel cell 100 shown
in FIG. 17. FIG. 19 is a schematic diagram showing a schematic
configuration of the cathode separator 30 of the fuel cell 100
shown in FIG. 17. In FIGS. 18 and 19, a vertical direction of each
of the anode separator 20 and the cathode separator 30 is shown as
a vertical direction of the drawing.
[0240] First, the configuration of the anode separator 20 will be
explained in detail in reference to FIGS. 17 and 18.
[0241] As shown in FIG. 18, the anode separator 20 is formed to
have a plate shape and a substantially quadrangular (herein,
rectangular) shape. Respective manifold holes, such as the fuel gas
supplying manifold hole 31, are formed at a peripheral portion of
the anode separator 20 to penetrate the anode separator 20 in the
thickness direction. Specifically, the oxidizing gas supplying
manifold hole (first reactant gas supplying manifold hole) 33 is
formed at an upper portion of one side portion (hereinafter
referred to as "first side portion") of the anode separator 20, and
the cooling fluid discharging manifold hole 36 is formed below the
oxidizing gas supplying manifold hole 33. Moreover, the cooling
fluid supplying manifold hole 35 is formed on an upper inner side
of the oxidizing gas supplying manifold hole 33 of the first side
portion. Similarly, the fuel gas discharging manifold hole 32 is
formed on a lower inner side of the cooling fluid discharging
manifold hole 36. Further, the fuel gas supplying manifold hole
(second reactant gas supplying manifold hole) 31 is formed at an
upper portion of the other side portion (hereinafter referred to as
"second side portion") of the anode separator 20, and the oxidizing
gas discharging manifold hole 34 is formed below the fuel gas
supplying manifold hole 31.
[0242] The fuel gas supplying manifold hole 31 and the oxidizing
gas supplying manifold hole 33 are formed to sandwich a central
portion of the anode separator 20 and be opposed to each other.
Here, the central portion of the anode separator 20 denotes a
center portion with respect to an outer peripheral portion of the
anode separator 20.
[0243] Then, as shown in FIG. 18, the groove-like fuel gas channel
27 is formed in a serpentine shape on the inner surface of the
anode separator 20 so as to connect the fuel gas supplying manifold
hole 31 and the fuel gas discharging manifold hole 32. Herein, the
fuel gas channel 27 is constituted by one groove, and this groove
is essentially constituted by reciprocating portions 127A and
inverting portions 127B.
[0244] Specifically, the groove constituting the fuel gas channel
27 extends in the horizontal direction from the fuel gas supplying
manifold hole 31 toward the first side portion by a certain
distance, extends downward therefrom by a certain distance, extends
therefrom in the horizontal direction toward the second side
portion by a certain distance, and extends downward therefrom by a
certain distance. This pattern is repeated twelve times, and the
groove further extends therefrom in the horizontal direction toward
the first side portion by a certain distance, and extends downward
therefrom to reach the fuel gas discharging manifold hole 32. Thus,
portions of the fuel gas channel 27 which portions extend in the
horizontal direction constitute the reciprocating portions 127A,
and portions of the fuel gas channel 27 which portions extend
downward constitute the inverting portions 127B.
[0245] As shown in FIGS. 17 and 18, a portion between the grooves
constituting the fuel gas channel 27 forms the rib portion 29
contacting the anode 4.
[0246] Next, the configuration of the cathode separator 30 will be
explained in detail in reference to FIGS. 17 and 19.
[0247] As shown in FIG. 19, the cathode separator 30 is formed to
have a plate shape and a substantially quadrangular (herein,
rectangular) shape. Respective manifold holes, such as the fuel gas
supplying manifold hole 31, are formed at a peripheral portion of
the cathode separator 30 to penetrate the cathode separator 30 in
the thickness direction. The arrangement of the manifold holes of
the cathode separator 30 is the same as that of the anode separator
20, so that a detailed explanation thereof is omitted.
[0248] As shown in FIG. 19, the groove-like oxidizing gas channel
37 is formed in a serpentine shape on the inner surface of the
cathode separator 30 so as to connect the oxidizing gas supplying
manifold hole 33 and the oxidizing gas discharging manifold hole
34. The oxidizing gas channel 37 and the fuel gas channel 27 are
configured to form so-called parallel flow. Here, the parallel flow
will be explained in reference to FIG. 20.
[0249] FIG. 20 is a schematic diagram showing the configurations of
the anode separator 20 and cathode separator 30 of the fuel cell
100 shown in FIG. 17. FIG. 20 transparently shows the anode
separator 20 and the cathode separator 30 when viewed from the
thickness direction of the fuel cell 100. Moreover, in FIG. 20,
each of the groove of the fuel gas channel 27 of the anode
separator 20 and the groove of the oxidizing gas channel 37 of the
cathode separator 30 is typically shown by a single line, and a
vertical direction of each of the separators 20 and 30 is shown as
a vertical direction of the drawing. Further, in FIG. 20, the
positions of the fuel gas channel 27 and the oxidizing gas channel
37 are displaced each other in the vertical direction to facilitate
visualization of these channels 27 and 37.
[0250] As shown in FIG. 20, the fuel gas channel 27 and the
oxidizing gas channel 37 partially have a portion where the
oxidizing gas and the fuel gas flow in opposite directions.
However, a configuration in which the overall flow direction of the
oxidizing gas flowing from upstream to downstream and the overall
flow direction of the fuel gas flowing from upstream to downstream
macroscopically (wholly) coincide with each other when viewed from
the thickness direction of the fuel cell 100 is called "parallel
flow".
[0251] Moreover, as shown in FIG. 19, the oxidizing gas channel 37
is constituted by a single groove, and the groove is essentially
constituted by reciprocating portions 137C and inverting portions
137B. Specifically, the groove constituting the oxidizing gas
channel 37 extends in the horizontal direction from the oxidizing
gas supplying manifold hole 33 toward the second side portion by a
certain distance, extends downward therefrom by a certain distance,
extends therefrom in the horizontal direction toward the first side
portion by a certain distance, and extends downward therefrom by a
certain distance. This pattern is repeated thirteen times, and the
groove further extends in the horizontal direction toward the
second side portion by a certain distance, and extends downward
therefrom to reach the oxidizing gas discharging manifold hole 34.
Thus, portions of the oxidizing gas channel 37 which portions
extend in the horizontal direction constitute the reciprocating
portions 137C, and portions of the oxidizing gas channel 37 which
portions extend downward constitute the inverting portions 137B. A
portion between the grooves constituting the oxidizing gas channel
37 forms the rib portion 39 contacting the cathode 8.
[0252] Further, as shown in FIGS. 17, 19, and 20, the oxidizing gas
channel 37 includes an uppermost stream portion 37C and a
downstream portion 37D. The uppermost stream portion 37C is
constituted by a channel formed at an uppermost stream portion 30E
of the cathode separator 30. The uppermost stream portion 30E is
located between a portion 37E and a portion 27E when viewed from
the thickness direction of the cathode separator 30. The portion
37E is a portion where the oxidizing gas channel 37 extending from
its upstream end first contacts the cathode 8. The portion 27E is a
portion where the fuel gas channel 27 extending from its upstream
end first contacts the anode 4. In other words, the uppermost
stream portion 37C is a portion extending from the portion 37E of
the oxidizing gas channel 37 to a portion where the oxidizing gas
channel 37 overlapping the fuel gas channel 27 first separates from
the fuel gas channel 27. Herein, the uppermost stream portion 37C
is a portion extending from the portion 37E of the oxidizing gas
channel 37 to a point where the oxidizing gas channel 37 extending
toward the second side portion in the horizontal direction has
reached (to be specific, a portion extending from the portion 37E
of the oxidizing gas channel 37 to a downstream end of the first
reciprocating portion 137A). Moreover, the downstream portion 37D
is a portion provided downstream of the uppermost stream portion
37C of the oxidizing gas channel 37.
[0253] Then, the width of the entire uppermost stream portion 37C
is constant, the width of the entire downstream portion 37D is also
constant, and the width of the entire uppermost stream portion 37C
is smaller than the width of the downstream portion 37D. Moreover,
the depth of the uppermost stream portion 37C is larger than the
depth of the downstream portion 37D, and the cross-sectional area
(hereinafter simply referred to as "channel cross-sectional area")
of the groove of the uppermost stream portion 37C in a direction
perpendicular to the flow of the oxidizing gas is substantially the
same as the channel cross-sectional area of the downstream portion
37D. With this, the pressure loss in the uppermost stream portion
37C of the oxidizing gas channel 37 and the pressure loss in the
downstream portion 37D of the oxidizing gas channel 37 become the
same as each other, so that the flow rate of the oxidizing gas
flowing through the uppermost stream portion 37C and the flow rate
of the oxidizing gas flowing through the downstream portion 37D
become essentially the same as each other.
[0254] Herein, the width of the portion extending from the upstream
end of the oxidizing gas channel 37 to the portion 37E is set to be
the same as the width of the uppermost stream portion 37C. However,
the present invention is not limited to this, and the width of the
portion extending from the upstream end of the oxidizing gas
channel 37 to the portion 37E may be set to be the same as the
width of the downstream portion 37D or may be set to be different
from the width of the uppermost stream portion 37C or the
downstream portion 37D.
[0255] Next, operational advantages of the polymer electrolyte fuel
cell 100 according to Embodiment 5 will be explained in reference
to FIGS. 17 to 20.
[0256] Operational Advantages of Polymer Electrolyte Fuel Cell
[0257] As described above, the water content of a portion of the
cathode 8 which portion faces the oxidizing gas channel 37 becomes
lower than the water content of a portion of the cathode 8 which
portion contacts the rib portion 39. Especially when the fuel cell
100 is driven at high temperature and low humidity, the water
content of a portion 8A of the cathode 8 which portion faces the
uppermost stream portion 37C of the oxidizing gas channel 37 is
low. On this account, a portion of the polymer electrolyte membrane
1 (hereinafter referred to as "uppermost stream portion of the
polymer electrolyte membrane 1") which portion is opposed to the
uppermost stream portion 37C of the oxidizing gas channel 37 tends
to dry, so that the polymer electrolyte membrane 1 may
deteriorate.
[0258] However, in the fuel cell 100 according to Embodiment 5,
since the width of the uppermost stream portion 37C of the
oxidizing gas channel 37 is smaller than the width of the
downstream portion 37D of the oxidizing gas channel 37, the portion
8A whose water content is low is small in size. On this account,
the drying of the uppermost stream portion of the polymer
electrolyte membrane 1 can be suppressed, so that the deterioration
of the polymer electrolyte membrane 1 can be suppressed.
[0259] Meanwhile, since the width of the downstream portion 37D of
the oxidizing gas channel 37 is larger than the width of the
uppermost stream portion 37C of the oxidizing gas channel 37, the
water content of a portion of the cathode 8 which portion faces the
downstream portion 37D becomes low. With this, especially when the
fuel cell 100 according to Embodiment 5 is driven at high
temperature and high humidity, the flooding of the portion of the
cathode 8 which portion faces the downstream portion 37D can be
suppressed.
[0260] Moreover, in the fuel cell 100 according to Embodiment 5,
since the cross-sectional area of the uppermost stream portion 37C
of the oxidizing gas channel 37 is substantially the same as the
cross-sectional area of the downstream portion 37D of the oxidizing
gas channel 37, the pressure loss in the uppermost stream portion
37C of the oxidizing gas channel 37 and the pressure loss in the
downstream portion 37D of the oxidizing gas channel 37 become the
same as each other. On this account, the flow rate of the oxidizing
gas flowing through the uppermost stream portion 37C of the
oxidizing gas channel 37 and the flow rate of the oxidizing gas
flowing through the downstream portion 37D of the oxidizing gas
channel 37 can be set to be essentially the same as each other.
Embodiment 6
[0261] FIG. 21 is a cross-sectional view schematically showing a
schematic configuration of the cathode separator of the fuel cell
according to Embodiment 6 of the present invention. In FIG. 21, a
part of the cathode separator is omitted.
[0262] As shown in FIG. 21, the fuel cell according to Embodiment 6
of the present invention is the same in basic configuration as the
fuel cell 100 according to Embodiment 5, but the configuration of
the oxidizing gas channel 37 of the cathode separator 30 is
different as below.
[0263] To be specific, the downstream portion 37D of the oxidizing
gas channel 37 of the cathode separator 30 of the fuel cell
according to Embodiment 6 is formed such that the cross section
thereof in a direction perpendicular to the flow of the oxidizing
gas has a substantially trapezoidal shape, and an opening area
thereof is larger than the opening area of the uppermost stream
portion 37C. With this, the cross-sectional area of the channel of
the uppermost stream portion 37C and the cross-sectional area of
the channel of the downstream portion 37D can be set to be
essentially the same as each other without setting the depth of the
uppermost stream portion 37C to be larger than the depth of the
downstream portion 37D. The cross-sectional area of the uppermost
stream portion 37C and the cross-sectional area of the downstream
portion 37D being essentially the same as each other denotes that
the pressure loss of the oxidizing gas flowing through the
uppermost stream portion 37C and the pressure loss of the oxidizing
gas flowing through the downstream portion 37D are essentially the
same as each other.
[0264] Even with this configuration, the fuel cell according to
Embodiment 6 obtains the same operational advantages as the fuel
cell 100 according to Embodiment 5.
Embodiment 7
[0265] FIG. 22 is a cross-sectional view schematically showing a
schematic configuration of the cathode separator of the fuel cell
according to Embodiment 7 of the present invention. In FIG. 22, a
part of the cathode separator is omitted.
[0266] As shown in FIG. 22, the fuel cell according to Embodiment 7
of the present invention is the same in basic configuration as the
fuel cell 100 according to Embodiment 5, but the configuration of
the oxidizing gas channel 37 of the cathode separator 30 is
different as below.
[0267] To be specific, the downstream portion 37D of the oxidizing
gas channel 37 of the cathode separator 30 of the fuel cell
according to Embodiment 7 is formed such that a peripheral surface
of the groove thereof has a step shape so as to spread outward, and
the opening area thereof is larger than the opening area of the
uppermost stream portion 37C. In other words, the edge portion of
the rib portion 39 formed by the downstream portion 37D is
chamfered.
[0268] With this, the cross-sectional area of the uppermost stream
portion 37C and the cross-sectional area of the downstream portion
37D can be set to be essentially the same as each other without
setting the depth of the uppermost stream portion 37C to be larger
than the depth of the downstream portion 37D.
[0269] Even with this configuration, the fuel cell according to
Embodiment 7 obtains the same operational advantages as the fuel
cell 100 according to Embodiment 5.
Embodiment 8
[0270] FIG. 23 is a cross-sectional view schematically showing a
schematic configuration of the cathode separator of the fuel cell
according to Embodiment 8 of the present invention. In FIG. 23, a
part of the cathode separator is omitted.
[0271] As shown in FIG. 23, the fuel cell according to Embodiment 8
of the present invention is the same in basic configuration as the
fuel cell 100 according to Embodiment 5, but the configuration of
the oxidizing gas channel 37 of the cathode separator 30 is
different as below.
[0272] To be specific, the uppermost stream portion 37C of the
oxidizing gas channel 37 of the cathode separator 30 of the fuel
cell according to Embodiment 8 is formed such that a peripheral
surface of the groove thereof has a step shape, an opening portion
of the groove thereof concaves inwardly, and the opening area
thereof is larger than the opening area of the downstream portion
37D. With this, the cross-sectional area of the uppermost stream
portion 37C and the cross-sectional area of the downstream portion
37D can be set to be essentially the same as each other without
setting the depth of the uppermost stream portion 37C to be larger
than the depth of the downstream portion 37D.
[0273] Even with this configuration, the fuel cell according to
Embodiment 8 obtains the same operational advantages as the fuel
cell 100 according to Embodiment 5.
Embodiment 9
[0274] FIG. 24 is a cross-sectional view schematically showing a
schematic configuration of the fuel cell according to Embodiment 9
of the present invention. FIG. 25 is a schematic diagram showing a
schematic configuration of the anode separator of the fuel cell
shown in FIG. 24. In FIG. 24, a part of the fuel cell is omitted.
In FIG. 25, a vertical direction of the anode separator is shown as
a vertical direction of the drawing.
[0275] As shown in FIGS. 24 and 25, the fuel cell 100 according to
Embodiment 9 and the fuel cell 100 according to Embodiment 5 are
the same in basic configuration as each other, but are different
from each other in that the width of the uppermost stream portion
37C of the oxidizing gas channel 37 of the cathode separator 30 and
the width of the downstream portion 37D of the oxidizing gas
channel 37 of the cathode separator 30 are substantially the same
as each other, and the depth of the uppermost stream portion 37C
and the depth of the downstream portion 37D are substantially the
same as each other. In addition, the configuration of the fuel gas
channel 27 of the anode separator 20 is different.
[0276] Specifically, as shown in FIG. 25, the fuel gas channel 27
includes an uppermost stream portion 27C and a downstream portion
27D. The uppermost stream portion 27C is constituted by a channel
formed at an uppermost stream portion 20E (see FIG. 20) of the
anode separator 20. The uppermost stream portion 20E (see FIG. 20)
of the anode separator 20 is located between the portion 27E and
the portion 37E when viewed from the thickness direction of the
anode separator 20. The portion 27E is a portion where the fuel gas
channel 27 extending from its upstream end first contacts the anode
4. The portion 37E is a portion where the oxidizing gas channel 37
extending from its upstream end first contacts the cathode 8. In
other words, the uppermost stream portion 27C is a portion
extending from the portion 27E of the fuel gas channel 27 to a
portion where the fuel gas channel 27 overlapping the oxidizing gas
channel 37 first separates from the oxidizing gas channel 37.
Herein, the uppermost stream portion 27C is a portion extending
from the upstream end of the fuel gas channel 27 to a portion where
the fuel gas channel 27 extending toward the second side portion in
the horizontal direction has reached (to be specific, a portion
extending from the portion 27E of the fuel gas channel 27 to a
downstream end of the first reciprocating portion 127A). Moreover,
the downstream portion (remaining portion) 27D is a portion
provided downstream of the uppermost stream portion 27C of the fuel
gas channel 27.
[0277] Then, the width of the entire uppermost stream portion 27C
is constant, the width of the entire downstream portion 27D is also
constant, and the width of the uppermost stream portion 27C is
smaller than the width of the downstream portion 27D. Moreover, the
depth of the uppermost stream portion 27C is larger than the depth
of the downstream portion 27D, and the cross-sectional area
(hereinafter simply referred to as "channel cross-sectional area")
of the groove of the uppermost stream portion 27C in the direction
perpendicular to the flow of the fuel gas is substantially the same
as the channel cross-sectional area of the downstream portion 27D.
With this, the pressure loss in the uppermost stream portion 27C of
the fuel gas channel 27 and the pressure loss in the downstream
portion 27D of the fuel gas channel 27 become the same as each
other, so that the flow rate of the fuel gas flowing through the
uppermost stream portion 27C and the flow rate of the fuel gas
flowing through the downstream portion 27D become essentially the
same as each other.
[0278] In the fuel cell 100 according to Embodiment 9 configured as
above, since the width of the uppermost stream portion 27C of the
fuel gas channel 27 is narrower than the width of the downstream
portion 27D of the fuel gas channel 27, a portion 4A, whose water
content is low, of the anode 4 is small in size. On this account,
the drying of a portion of the polymer electrolyte membrane 1 which
portion is opposed to the uppermost stream portion 27C of the fuel
gas channel 27 can be suppressed, so that the deterioration of the
polymer electrolyte membrane 1 can be suppressed.
[0279] Meanwhile, since the width of the downstream portion 27D of
the fuel gas channel 27 is larger than the width of the uppermost
stream portion 27C of the fuel gas channel 27, the water content of
a portion of the anode 4 which portion faces the downstream portion
27D becomes low. With this, especially when the fuel cell 100
according to Embodiment 9 is driven at high temperature and high
humidity, the flooding of the portion of the anode 4 which portion
faces the downstream portion 27D can be suppressed.
[0280] Moreover, in the fuel cell 100 according to Embodiment 9,
since the cross-sectional area of the uppermost stream portion 27C
of the fuel gas channel 27 is substantially the same as the
cross-sectional area of the downstream portion 27D of the fuel gas
channel 27, the pressure loss in the uppermost stream portion 27C
of the fuel gas channel 27 and the pressure loss in the downstream
portion 27D of the fuel gas channel 27 become the same as each
other. On this account, the flow rate of the fuel gas flowing
through the uppermost stream portion 27C of the fuel gas channel 27
and the flow rate of the fuel gas flowing through the downstream
portion 27D of the fuel gas channel 27 can be set to be essentially
the same as each other.
[0281] The fuel gas channel 27 may be formed in the same shape as
the oxidizing gas channel 37 of Embodiments 6 to 8.
Embodiment 10
[0282] FIG. 26 is a cross-sectional view schematically showing a
schematic configuration of the fuel cell according to Embodiment 10
of the present invention. In FIG. 26, a part of the fuel cell is
omitted.
[0283] As shown in FIG. 26, the fuel cell 100 according to
Embodiment 10 of the present invention and the fuel cell 100
according to Embodiment 5 are the same in basic configuration as
each other, but are different from each other in that the fuel gas
channel 27 of the anode separator 20 is configured in the same
manner as the fuel gas channel 27 of the anode separator 20 of the
fuel cell 100 according to Embodiment 9.
[0284] With this configuration, the fuel cell 100 according to
Embodiment 10 of the present invention obtains the same operational
advantages as the fuel cell 100 according to Embodiment 5 and
obtains the same operational advantages as the fuel cell 100
according to Embodiment 9.
Embodiment 11
[0285] FIG. 27 is a cross-sectional view schematically showing a
schematic configuration of the fuel cell according to Embodiment 11
of the present invention. In FIG. 27, a part of the fuel cell is
omitted.
[0286] As shown in FIG. 27, the fuel cell 100 according to
Embodiment 11 of the present invention is the same in basic
configuration as the fuel cell 100 according to Embodiment 10, but
the rib portion 37 formed by the oxidizing gas channel 37 and the
rib portion 27 formed by the fuel gas channel 27 are different as
below.
[0287] To be specific, the width of the rib portion 39A formed
between the groove constituting the uppermost stream portion 37C of
the oxidizing gas channel 37 and the groove constituting the
downstream portion 37D of the oxidizing gas channel 37 is larger
than the width of the rib portion 39B formed by only the groove
constituting the downstream portion 37D. Similarly, the width of
the rib portion 29A formed between the groove constituting the
uppermost stream portion 27C of the fuel gas channel 27 and the
groove constituting the downstream portion 27D of the fuel gas
channel 27 is larger than the width of the rib portion 29B formed
by only the groove constituting the downstream portion 27D.
[0288] With this configuration, the fuel cell 100 according to
Embodiment 11 of the present invention obtains the same operational
advantages as the fuel cell 100 according to Embodiment 10.
[0289] Further, in the fuel cell 100 according to Embodiment 11,
since the contact area between the rib portion 39B of the cathode
separator 30 and the cathode 8 (to be precise, the cathode gas
diffusion layer 7) is smaller than the contact area between the rib
portion 39A and the cathode 8, the amount of heat transferred from
the cathode 8 (to be precise, the cathode catalyst layer 6 (see
FIG. 6)) to the cathode separator 30 becomes small, so that the
cathode gas diffusion layer 7 opposed to the downstream portion 37D
of the oxidizing gas channel 37 becomes high in temperature. On
this account, the dew condensation of the water generated by the
electric power generating reaction is less likely to occur, and the
occurrence of the flooding in the downstream portion 37D of the
oxidizing gas channel 37 is suppressed. In addition, the occurrence
of the flooding in the cathode gas diffusion layer 7 is also
suppressed. Similarly, since the contact area between the rib
portion 29B of the anode separator 20 and the anode 4 (to be
precise, the anode gas diffusion layer 3) is smaller than the
contact area between the rib portion 29A and the anode 4, the
occurrence of the flooding in the downstream portion 27D of the
fuel gas channel 27 is suppressed, and the occurrence of the
flooding in the anode gas diffusion layer 3 is also suppressed.
[0290] Meanwhile, in the uppermost stream portion 37C of the
oxidizing gas channel 37, by increasing the contact area between
the rib portion 39A and the cathode 8, the contact resistance is
reduced, and the decrease in the battery voltage is suppressed.
Similarly, in the uppermost stream portion 27C of the fuel gas
channel 27, by increasing the contact area between the rib portion
29A and the anode 4, the contact resistance is reduced, and the
decrease in the battery voltage is suppressed.
[0291] In the present embodiment, the width of the rib portion 29A
is set to be larger than the width of the rib portion 29B, and the
width of the rib portion 39A is set to be larger than the width of
the rib portion 39B. However, the present embodiment is not limited
to this, and only the width of the rib portion 29A may be set to be
larger than the width of the other rib portion, or only the width
of the rib portion 39A may be set to be larger than the width of
the other rib portion.
Embodiment 12
[0292] FIG. 28 is a schematic diagram showing a schematic
configuration of the anode separator of the fuel cell according to
Embodiment 12 of the present invention. FIG. 29 is a schematic
diagram showing a schematic configuration of the cathode separator
of the fuel cell according to Embodiment 12 of the present
invention. In FIGS. 28 and 29, a vertical direction of each of the
anode separator and the cathode separator is shown as a vertical
direction of the drawing.
[0293] As shown in FIGS. 28 and 29, the fuel cell according to
Embodiment 12 of the present invention and the fuel cell 100
according to Embodiment 10 are the same in basic configuration as
each other, but are different from each other in that each of the
fuel gas channel 27 of the anode separator 20 and the oxidizing gas
channel 37 of the cathode separator 30 is formed to have a spiral
shape. Since the fuel gas channel 27 is configured in the same
manner as the oxidizing gas channel 37, the following will explain
the oxidizing gas channel 37.
[0294] Specifically, as shown in FIG. 29, the oxidizing gas channel
37 is essentially constituted by horizontal portions 137C formed to
extend in the horizontal direction and vertical portions 137B
formed to extend in the vertical direction. The oxidizing gas
channel 37 extends so as to converge from the peripheral portion to
the central portion of the cathode separator 30 in a clockwise
direction, turn round at the central portion of the cathode
separator 30, and spread toward the peripheral portion of the
cathode separator 30 in a counterclockwise direction.
[0295] Herein, the uppermost stream portion 37C of the oxidizing
gas channel 37 is constituted by a channel extending between the
portion 37E where the oxidizing gas channel 37 extending from its
upstream end first contacts the cathode 8 and a portion where the
oxidizing gas channel 37 extending toward the second side portion
in the horizontal direction has reached (in other words, the
uppermost stream portion 37C is a portion extending from the
portion 37E of the oxidizing gas channel 37 to a downstream end of
the first horizontal portion 137C). Moreover, the width of the
entire uppermost stream portion 37C of the oxidizing gas channel 37
is constant, the width of the entire downstream portion 37D is
constant, and the width of the uppermost stream portion 37C is
smaller than the width of the downstream portion 37D.
[0296] Even with this configuration, the fuel cell according to
Embodiment 12 of the present invention obtains the same operational
advantages as the fuel cell 100 according to Embodiment 10.
[0297] In the present embodiment, each of the fuel gas channel 27
and the oxidizing gas channel 37 is formed to have a spiral shape.
However, the present embodiment is not limited to this, and only
the fuel gas channel 27 may be formed to have a spiral shape, or
only the oxidizing gas channel 37 may be formed to have a spiral
shape.
Embodiment 13
[0298] FIG. 30 is a schematic diagram showing a schematic
configuration of the anode separator of the fuel cell according to
Embodiment 13 of the present invention. FIG. 31 is a schematic
diagram showing a schematic configuration of the cathode separator
of the fuel cell according to Embodiment 13 of the present
invention. In FIGS. 30 and 31, a vertical direction of each of the
anode separator and the cathode separator is shown as a vertical
direction of the drawing.
[0299] The fuel cell according to Embodiment 13 of the present
invention and the fuel cell 100 according to Embodiment 10 are the
same in basic configuration as each other, but are different from
each other in that as shown in FIGS. 30 and 31, each of the fuel
gas channel 27 and the oxidizing gas channel 37 is constituted by a
plurality of grooves (herein, the fuel gas channel 27 is
constituted by two grooves, and the oxidizing gas channel 37 is
constituted by three grooves). Moreover, the fuel cell according to
Embodiment 13 of the present invention is different from the fuel
cell 100 according to Embodiment 10 in that: the uppermost stream
portion 27C of the fuel gas channel 27 is constituted by a channel
extending between the portion 27E where the fuel gas channel 27
extending from its upstream end first contacts the anode 4 and a
point where the fuel gas channel 27 extending toward the first side
portion in the horizontal direction has reached (in other words, a
portion extending from the portion 27E of the fuel gas channel 27
to the downstream end of the first reciprocating portion 127A); and
the uppermost stream portion 37C of the oxidizing gas channel 37 is
constituted by a channel extending between the portion 37E where
the oxidizing gas channel 37 extending from its upstream end first
contacts the cathode 8 and a point where the oxidizing gas channel
37 extending toward the second side portion in the horizontal
direction has reached (in other words, a portion extending from the
portion 37E of the oxidizing gas channel 37 to the downstream end
of the first reciprocating portion 137C).
[0300] Even with this configuration, the fuel cell according to
Embodiment 13 obtains the same operational advantages as the fuel
cell 100 according to Embodiment 10.
Embodiment 14
[0301] FIG. 32 is a schematic diagram showing a schematic
configuration of the anode separator of the fuel cell according to
Embodiment 14 of the present invention. FIG. 33 is a schematic
diagram showing a schematic configuration of the cathode separator
of the fuel cell according to Embodiment 14 of the present
invention. In FIGS. 32 and 33, a vertical direction of each of the
anode separator and the cathode separator is shown as a vertical
direction of the drawing.
[0302] The fuel cell according to Embodiment 14 of the present
invention and the fuel cell according to Embodiment 13 are the same
in basic configuration as each other, but are different from each
other in that as shown in FIGS. 32 and 33, each of the fuel gas
channel 27 and the oxidizing gas channel 37 is formed to have a
spiral shape. Moreover, the fuel cell according to Embodiment 14
and the fuel cell according to Embodiment 13 are different from
each other in that each of the uppermost stream portion 27C of the
fuel gas channel 27 and the uppermost stream portion 37C of the
oxidizing gas channel 37 is constituted by a channel extending from
the upstream end of the fuel gas channel 27 or the oxidizing gas
channel 37 to a portion where the fuel gas channel 27 or the
oxidizing gas channel 37 extending toward the second side portion
in the horizontal direction has reached (in other words, the
uppermost stream portion 27C or 37C is a portion extending from the
upstream end of the fuel gas channel 27 or the oxidizing gas
channel 37 to the downstream end of the first horizontal
portion).
[0303] Even with this configuration, the fuel cell according to
Embodiment 14 of the present invention obtains the same operational
advantages as the fuel cell according to Embodiment 13.
Embodiment 15
[0304] FIG. 34 is a schematic diagram showing a schematic
configuration of the anode separator of the fuel cell according to
Embodiment 15 of the present invention. FIG. 35 is a schematic
diagram showing a schematic configuration of the cathode separator
of the fuel cell according to Embodiment 15 of the present
invention. In FIGS. 34 and 35, a vertical direction of each of the
anode separator and the cathode separator is shown as a vertical
direction of the drawing. In FIG. 34, only the fuel gas supplying
manifold hole 31 and the fuel gas discharging manifold hole 32 are
shown, and the other manifold holes are not shown. In FIG. 35, only
the oxidizing gas supplying manifold hole 33 and the oxidizing gas
discharging manifold hole 34 are shown, and the other manifold
holes are not shown.
[0305] The fuel cell according to Embodiment 15 of the present
invention and the fuel cell according to Embodiment 14 are the same
in basic configuration as each other, but are different from each
other in that as shown in FIGS. 32 and 33, each of the anode
separator 20 and the cathode separator 30 is formed to have a
circular plate shape. Moreover, the fuel cell according to
Embodiment 15 and the fuel cell according to Embodiment 14 are
different from each other in that the fuel gas supplying manifold
hole 31 and the fuel gas discharging manifold hole 32 are formed to
sandwich a central portion (central axis 71) of the anode separator
20 and be opposed to each other, and similarly, the oxidizing gas
supplying manifold hole 32 and the oxidizing gas discharging
manifold hole 33 are formed to sandwich a central portion (central
axis 71) of the cathode separator 30 and be opposed to each
other.
[0306] Moreover, the fuel gas channel 27 of the fuel cell according
to Embodiment 15 extends so as to converge in an arc from an
upstream end thereof to the central portion of the anode separator
20 in a clockwise direction, turn round at the central portion of
the anode separator 20, and spread in an arc toward the peripheral
portion of the anode separator 20 in a counterclockwise direction.
Similarly, the oxidizing gas channel 37 extends so as to converge
in an arc from an upstream end thereof to the central portion of
the cathode separator 30 in a clockwise direction, turn round at
the central portion of the cathode separator 30, and spread in an
arc toward the peripheral portion of the cathode separator 30 in a
counterclockwise direction.
[0307] Further, the fuel cell according to Embodiment 15 is
different from the fuel cell according to Embodiment 14 in that:
the uppermost stream portion 27C of the fuel gas channel 27 is
constituted by a channel extending between the portion 27E where
the fuel gas channel 27 extending from its upstream end first
contacts the anode 4 to a portion where the fuel gas channel 27
extending half round from its upstream end has reached; and the
uppermost stream portion 37C of the oxidizing gas channel 37 is
constituted by a channel extending between the portion 37E where
the oxidizing gas channel 37 extending from its upstream end first
contacts the cathode 8 and a portion where the oxidizing gas
channel 37 extending half round from its upstream end has
reached.
[0308] Even with this configuration, the fuel cell according to
Embodiment 15 obtains the same operational advantages as the fuel
cell according to Embodiment 14.
[0309] In the above embodiments, a so-called inner manifold type in
which respective manifold holes are formed on the separator is
adopted as the fuel cell stack. However, the present embodiments
are not limited to this, and an outer manifold type may be adopted
as the fuel cell stack.
[0310] Moreover, in the above embodiments, the fuel gas supplying
manifold hole 31 and the oxidizing gas supplying manifold hole 33
are formed to be opposed to each other. However, the present
embodiments are not limited to this, and the fuel gas supplying
manifold hole 31 and the oxidizing gas supplying manifold hole 33
may be formed to be adjacent to each other.
[0311] Further, in the above embodiments, each of the width of the
entire uppermost stream portion 27C of the fuel gas channel 27, the
width of the entire uppermost stream portion 37C of the oxidizing
gas channel 37, the width of the entire downstream portion 27D of
the fuel gas channel 27, and the width of the entire downstream
portion 37D of the oxidizing gas channel 37 is constant. However,
the present embodiments are not limited to this. As long as the
operational advantages of the present invention can be obtained,
the width of a part of the uppermost stream portion 27C, 37C and/or
the width of a part of the downstream portion 27D, 37D may be
changed, the width of a part of the uppermost stream portion 27C,
37C may be larger than the width of a part of the downstream
portion 27D, 37D, or the width of a part of the downstream portion
27D, 37D may be smaller than the width of a part of the uppermost
stream portion 27C, 37C.
[0312] From the foregoing explanation, many modifications and other
embodiments of the present invention are obvious to one skilled in
the art. Therefore, the foregoing explanation should be interpreted
only as an example, and is provided for the purpose of teaching the
best mode for carrying out the present invention to one skilled in
the art. The structures and/or functional details may be
substantially modified within the spirit of the present
invention.
INDUSTRIAL APPLICABILITY
[0313] The polymer electrolyte fuel cell and fuel cell stack of the
present invention are useful as a polymer electrolyte fuel cell and
fuel cell stack capable of adequately suppressing the flooding.
Moreover, the polymer electrolyte fuel cell and fuel cell stack of
the present invention are useful as a polymer electrolyte fuel cell
and fuel cell stack capable of suppressing the drying of the
polymer electrolyte membrane, and therefore, suppressing the
deterioration of the polymer electrolyte membrane when the polymer
electrolyte fuel cell is driven at high temperature and low
humidity.
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